Rearview mirror assemblies with anisotropic polymer laminates

ABSTRACT

Anisotropic film laminates for use in image-preserving reflectors such as rearview automotive mirror assemblies, and related methods of fabrication. A film may comprise an anisotropic layer such as a light-polarizing layer and other functional layers. The film having controlled water content is heated under omnidirectional pressure and vacuum to a temperature substantially equal to or above a lower limit of a glass-transition temperature range of the film so as to be laminated to a substrate. The laminate is configured as part of a mirror structure so as to increase contrast of light produced by a light source positioned behind the mirror structure and transmitted through the mirror structure towards a viewer. The mirror structure is devoid of any extended distortion and is characterized by SW and LW values less than 3, more preferably less than 2, and most preferably less than 1.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 12/774,721, filed May 5, 2010, which is acontinuation-in-part of U.S. patent application Ser. No. 12/629,757filed on Dec. 2, 2009, now U.S. Pat. No. 8,282,224, which is acontinuation-in-part of U.S. patent application Ser. No. 12/496,620filed on Jul. 1, 2009, now U.S. Pat. No. 8,545,030, which claimspriority from U.S. Provisional Applications Nos. 61/079,668 filed onJul. 10, 2008 and 61/093,608 filed on Sep. 2, 2008. The presentapplication claims priority from each of the above-mentionedapplications. The disclosures of each of the above-mentionedapplications are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to polymer-based film laminates and, moreparticularly, to automotive rearview mirrors incorporating laminatescomprising polymer-based film structures having an optically anisotropiclayer.

BACKGROUND ART

Mirror assemblies have proven to be a convenient location for providingdrivers with useful information. For example, a video display disposedbehind a mirror, but visible through a portion of the mirror, may supplythe driver with a video image of the scene to the rear of the vehiclewhere the driver's view may otherwise be obstructed. Similarly, aninformation display may offer the driver such vehicle-telemetryinformation as vehicle speed, engine status, oil level and temperature,for example, or any other information of interest. Integration of backupor other displays behind the automotive rearview mirror is generallypreferred over placing them adjacent to the mirror, thereby increasingthe area of the overall mirror assembly and impairing the driver's viewthrough the windshield.

Various types of displays incorporated within the rearview automotivemirror are known in the art, such as alphanumeric displays, graphicaldisplays, video displays, and combinations thereof. These displays arediscussed, for example, in U.S. Pat. No. 7,221,363, and in US PatentPublication No. 2008/0068520, each of which is incorporated herein inits entirety by reference. Displays that have been, or might be, used inautomotive applications employ various principles such as vacuumfluorescence (VF), electromechanics (EM), light emitting or organiclight emitting diodes (LED or OLED), plasma display panels (PDP),microelectromechanical systems (MEMS), electroluminescence (EL),projection (the projection systems include but are not limited to DLPand LCOS), or liquid crystal technology (used in liquid crystaldisplays, or LCDs), to name just a few. High-resolution LCDs capable ofdelivering color images, for example, may be mass-produced reliably andat low cost. LCDs are also noteworthy in that the liquid crystal mediumchanges its polarizing properties under the influence of the appliedelectric field and the light emanating from an LCD is polarized.

A particular challenge presented by display technology in an automotivecontext is that of providing the driver with sufficient luminance to seethe display clearly, especially under daunting conditions of ambientlight, while, at the same time, providing a clear and undistortedreflected view of the rear and peripheral scene to the driver. Sinceautomotive reflectors serve a crucial safety function in identifyingobjects otherwise outside of the driver's field of view, they mustcritically preserve image quality.

SUMMARY OF THE INVENTION

Embodiments of the invention provide an image-forming optical reflectorcomprising a base element (such as an electrochromic element or a prismelement) that reflects ambient light incident upon it, a light source,and a laminate that includes an anisotropic film disposed between thebase element and the light source. In one embodiment, the image-formingreflector may include a variable reflectance mirror system for use in arearview mirror assembly having a light source transmitting light of afirst polarization through the mirror system. The mirror system may be amulti-zone mirror system. The anisotropic film may extend across thefull field-of-view of the mirror system or, alternatively, it may extendsubstantially over only a transflective zone of the multi-zone systemthrough which the light source transmits light towards a viewer. Thefilm receives the light from the light source, transmitting a portion ofthis light that has a first polarization and reflecting a portion ofthis light that has a second polarization that is opposite to the firstpolarization. The mirror is substantially devoid of any extendeddistortion. In one embodiment, the mirror system is characterized bysurface values SW and LW, derived as discussed below, which do notexceed 3, preferably do not exceed 2 and most preferably do notexceed 1. The anisotropic film may be laminated between a substrate anda superstrate, which may be releasably adhered to the film. The lightsource may be a part of the laminate and may act as the superstrate.Alternatively or in addition, the base element may be a part of thelaminate and may act as the substrate. In a specific embodiment, thelaminate may be a stand-alone component of the reflector. The lightsource may comprise a display subassembly, for example an LCDsubassembly. In a specific embodiment, at least one of areflectance-enhancing and an opacifying layer may be additionallyemployed adjacent to a surface of the substrate and superstrate. Theopacifying layer may substantially cover a portion of the surface thatis located outside the transflective portion of the mirror structure.

Additional embodiments of the invention provide an optical element foroptimizing transmission of light through an image-forming opticalreflector. In a specific embodiment, the optical element of theinvention placed within the mirror system of the invention increases acontrast of light transmitted from a light source through the mirrorsystem to a viewer. The optical element may comprise an opticalsubstrate, having a surface, and a light-transmitting layered structureadhered to the surface, where the layered structure includes ananisotropic layer that transmits light of a first polarization andreflects light of a second polarization that is opposite to the firstpolarization. The anisotropic layer may be birefringent. Layers of thelayered structure, including the anisotropic layer, may each haveassociated glass transition temperatures, and the layered structure maybe characterized by a range of glass transition temperatures. In oneembodiment, the layered structure is characterized by SW and LW that donot exceed 3 after the layered structure has been heated to soften atleast a portion of the plastic film, which generally occurs at atemperature approaching or exceeding at least a lower glass-transitiontemperature from the range of glass transition temperatures associatedwith the layered structure. In another embodiment, after having beenheated to such softening temperature under uniform (and, preferably,substantially omnidirectional) pressure, the layered structure issubstantially devoid of any extended distortion. In one embodiment, theoptical element may be a laminate integrating at least a substrate andthe anisotropic layer. In another embodiment, the optical element mayadditionally comprise a light-transmitting optical superstrate disposedover the layered structure where the optical superstrate may or may notbe releasably coupled to the layered structure. The optical element issubstantially devoid of any extended distortion and may be characterizedby values SW and LW that do not exceed 3, preferably do not exceed 2 andmost preferably do not exceed 1. In a specific embodiment, the opticalreflector may be an image-forming reflector, for example a rearviewautomotive mirror.

In accordance with another embodiment of the invention, a method isprovided for fabricating a laminate containing an APBF for use in arearview mirror assembly. The method includes disposing a film structurecharacterized by a predetermined water content and having a layer withanisotropic optical properties on a substrate to form a composite. Themethod further includes applying heat and pressure at controlledhumidity levels and, optionally, vacuum to the composite underconditions causing formation of a laminate that comprises a part of theimage-forming and image-preserving reflector characterized by SW and LWvalues that are less than 3, preferably less than 2, and most preferablyless than 1. According to one embodiment of the invention it ispreferred that the water content of the APBF prior to lamination be lessthan about 0.6 weight-%, more preferably less than about 0.4 weight-%,even more preferably less than 0.2 weight-%, and most preferably lessthan about 0.1 weight-%. The temperature selected to laminate thecomposite may be within a range from about 50° C. to about 160° C.,preferably between about 80° C. to about 150° C., and most preferablybetween about 90° C. to about 110° C. The pressure chosen for laminationis preferably substantially omnidirectional and may be between about 25psi to about 2,500 psi, preferably from about 50 psi to about 500 psi,and most preferably from about 100 psi to about 400 psi. The filmstructure may be optionally stretched during the lamination process toassure adequate flatness of the film. In one embodiment, the fabricatedlaminate may be additionally annealed to enhance the strength of thelamination bond. In one embodiment, the layer with anisotropicproperties transmits light having a first polarization and reflectslight having a second polarization that is opposite to the firstpolarization, and the laminate is characterized by SW and LW values lessthan 3, preferably less than 2, and most preferably less than 1. Inanother embodiment, the laminate is substantially devoid of any extendeddistortion and the optical reflector comprising such laminate forms animage satisfying automotive industry standards.

In accordance with another embodiment, a switchable mirror system (SMS)for use in a vehicular rearview assembly equipped with a light sourcetransmitting light from within the rearview assembly through said SMS toa field-of-view (FOV) outside the assembly is provided. The SMS includesat least two electro-optic (EO) cells defined by at least threesequentially disposed spaced-apart glass substrates, a first EO-cellcorresponding to an outside portion of the rearview assembly and asecond EO-cell disposed between the first EO-cell and the light source.The first EO-cell is adapted to be a switchable linear absorptivepolarizer that attenuates light reflected from the second EO-cell, anddoes not substantially attenuate light transmitted from the light sourcethrough the second EO-cell. Further, the SMS has a reflectance valuethat is gradually variable in response to changes in voltages applied tothe first EO-cell, and as measured in said FOV in ambient light. Inaddition, the thicknesses of said at least three substrates are chosento provide for a net weight of said SMS per unit area of less than 2.0grams per cm².

In accordance with a further embodiment, a switchable mirror system(SMS) for use in a vehicular rearview assembly equipped with a lightsource transmitting light from within the rearview assembly through saidSMS to a field-of-view (FOV) outside the assembly is provided. The SMSincludes: a first electro-optic (EO) cell defined by two sequentiallydisposed spaced-apart substrates that corresponds to an outside portionof the rearview assembly; and a linear reflective polarizer disposedbetween the light source and the first EO-cell. The first EO-cell isadapted to be a switchable linear absorptive polarizer that attenuateslight reflected from the reflective polarizer and does not substantiallyattenuate light transmitted from the light source through the firstEO-cell. In addition, the SMS has a reflectance value that is graduallyvariable in response to changes in voltages applied to the first EOcell, and as measured in said FOV in ambient light.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be more readily understoodby reference to the following detailed description, taken with referenceto the accompanying, drawn not to scale, drawings where like featuresand elements are denoted by like numbers and labels, and in which:

FIG. 1 schematically illustrates an automotive rearview mirror assemblywith reduced optical quality resulting from a laminate that isfabricated conventionally and that is incorporated within the mirror.

FIG. 2 demonstrates an optical image formed in reflection from alaminate-containing display of a Nokia phone.

FIG. 3 is a flow-chart depicting steps of fabricating a laminate for usein an automotive rearview mirror assembly, in accordance with anembodiment of the invention. FIG. 3(A) illustrates an optionalpre-lamination treatment of a polymer-based film. FIG. 3(B) shows a stepof assembling a composite to be laminated. FIG. 3(C) illustrates a stepof lamination of the composite of FIG. 3(B). FIG. 3(D) depicts alaminate resulting from the lamination step of FIG. 3(C). FIG. 3(E)illustrates an optional step of releasing the superstrate of thelaminate, during or after the lamination procedure, resulting in analternative embodiment of the laminate as shown in FIG. 3(F). FIG. 3(G)schematically illustrates the steps of post-lamination processingincluding a step of inspection of the embodiments of FIGS. 3(D) and3(F), an optional step of post-lamination anneal, and an incorporationof an embodiment of a laminate into an automotive mirror assembly.

FIG. 4 schematically illustrates APBF-containing embodiments of rearviewmirror assemblies of the invention. FIG. 4(A): an APBF is laminated in arearview electrochromic mirror assembly. FIG. 4(B): an embodiment of theAPBF-laminate is incorporated, as a stand-alone component, into arearview tilt prism mirror assembly. FIGS. 4(C,D): an APBF is laminatedin a prism mirror assembly. FIG. 4(E): a display performs as a substrateof a laminate containing an APBF. FIGS. 4(F,G): an APBF-containinglaminate is integrated in a prism mirror structure containing a gap.FIG. 4(H): an APBF-containing laminate is integrated in a mirrorstructure containing a wedge-shaped gap. Light source is not shown inFIGS. 4(B-D, F-H).

FIG. 5 is a photograph of an electrochromic mirror assembly comprisingan embodiment of the laminate of the invention and forming an image of areference grid object positioned behind the viewer.

FIG. 6 presents a schematic cross-section of the embodiment of FIG. 5.

FIG. 7 shows auxiliary optional steps of the embodiment of the method ofthe invention illustrated in FIG. 3. FIG. 7(A): an arm of a press actsas a releasable superstrate. FIG. 7(B): a superstrate is attached to anarm of a press. FIG. 7(C): the use of a press-roll.

FIG. 8 shows reflecting structures pertaining to automotive rearviewmirror assemblies. FIG. 8(A) shows a prior art embodiment. FIG. 8(B)illustrates an embodiment of an APBF-containing laminate without asuperstrate. FIG. 8(C) illustrates an embodiment of an APBF-containinglaminate including a superstrate. FIGS. 8(D-G) show alternativeembodiments of lamination of an APBF between an EC-element and anadditional lite of glass. FIG. 8(H) demonstrates a perspective view ofanother embodiment of the invention. FIG. 8(I) shows another embodimentof the invention containing an APBF laminated between the EC-element andan additional lite of glass including a graded-thickness opacifyinglayer. FIG. 8(J) shows an embodiment similar to the embodiment of FIG.8(D) but including a stand-alone additional lite of glass with agraded-thickness opacifying layer disposed thereon.

FIG. 9 illustrates spectral dependences of reflectance characteristicsof embodiments of FIG. 8. FIG. 9(A) shows a reflectance curve for theembodiment of FIG. 8(B). FIG. 9(B) shows reflectance curves for theembodiments of FIGS. 8(B,C). FIG. 9(C) shows reflectance curves for theembodiments of FIGS. 8(C,D). FIG. 9(D) shows reflectance curves for theembodiments of FIGS. 8(D-G).

FIG. 10 graphically presents the date of Table 3.

FIG. 11 schematically illustrates the reflection and transmission ofambient light upon its interaction with an embodiment of the invention.

FIG. 12 shows the change in reflectance of the embodiment of FIG. 8(J)as a function of a position across the front surface of the embodiment.

FIG. 13 schematically illustrates embodiments used to enhance contrastof a display as perceived by a user wearing polarizing sunglasses. FIG.13(A): a light output from a conventionally oriented LCD is depolarized.FIG. 13(B): polarization of light output of a conventionally orientedLCD is rotated.

FIG. 14 depicts a photograph of a reference image formed according tothe visual evaluation test in reflection from another alternativeembodiment of the invention.

FIG. 15 illustrates experimentally measured results of the thermalanalysis of a DBEF-Q film, showing a glass transition temperatureregion.

FIG. 16 diagrammatically illustrates another APBF-laminate-containingmirror sample evaluated for extended distortions in the indicated areas.

FIG. 17 illustrates types of gradual edges in a chromium opacifyinglayer used with embodiments of the current invention. FIG. 17(A):Tapered gradient. FIG. 17(B): Feathered gradient. FIG. 17(C): Front viewof an opacifying layer with graded edges that limit the layer in ahorizontal direction. FIG. 17(D): Spatial distribution of thickness ofthe opacifying layer of FIG. 17(C).

FIG. 18 schematically illustrates, in side view, majorsubassembly-blocks of an automotive rearview mirror containing anelectronic device behind the mirror system.

FIG. 19 provides an example of the use of a reflective polarizercombined with a depolarizer in a conventional display application.

FIG. 20 shows an alternative embodiment of the present invention.

FIG. 21 shows alternative embodiments of the present invention. FIG.21(A): a laminate including a PSA and having a superstrate removed. FIG.21(B): a laminate including a PSA and having both a substrate and asuperstrate.

FIG. 22 shows yet another alternative embodiment of the presentinvention.

FIG. 23 shows another embodiment of the present invention.

FIG. 24 shows an embodiment including an opaque reflectance-enhancinglayer.

FIG. 25 shows an embodiment containing two angularly misalignedreflective polarizers.

FIG. 26 shows, in front view, an embodiment electrochromic mirrorassembly incorporating an embodiment of the present invention.

FIG. 27 shows a side view of the mirror assembly of FIG. 26.

FIG. 28 shows, in side view, an alternative embodiment of anelectrochromic mirror assembly incorporating an embodiment of a mirrorelement of the present invention.

FIG. 29(AB) illustrate a concept of a full-mirror display.

FIG. 30 shows an alternative embodiment of the invention where an APBFis laminated between a mirror element and an LCD that has its exit,absorbing polarizer removed.

FIG. 31 shows an alternative embodiment of the invention.

FIG. 32 shows embodiments of a prism mirror element with differentimplementations of a reflectance-enhancing layer.

FIG. 33 shows embodiments of a switchable mirror system of the inventionemploying an auxiliary LC-cell. FIG. 33 (A): two APBF-laminates areused. FIG. 33(B): an APBF-laminate and an absorptive polarizer are used.

FIG. 34 illustrates an embodiment of a switchable mirror system of theinvention that employs a combination of an LC-cell and an EC-element.

FIG. 35 shows an alternative embodiment of the invention.

FIG. 36 shows another alternative embodiment of the invention.

FIG. 37 shows refractive indices of materials used in constructing anembodiment of the invention.

FIG. 38 shows transmission and reflection spectra of an embodiment ofthe invention.

FIG. 39 shows transmission and reflection spectra of an alternativeembodiment of the invention.

FIG. 40 shows transmission and reflection spectra of another embodimentof the invention.

FIG. 41 shows transmission and reflection spectra of yet anotheralternative embodiment of the invention.

FIG. 42 shows transmittance characteristics of an embodiment of theinvention.

FIG. 43 shows transmittance characteristics of another embodiment of theinvention.

FIG. 44 demonstrates comparison of transmittance characteristics ofembodiments of FIGS. 42 and 43.

FIG. 45 provides illustrations to the concept of a segmented LC-cell.

FIGS. 46(A-H) provide examples of combinations of a polarizer used inconjunction with an LC-cell in various embodiments of the invention.

FIGS. 47(A,B) show transmission spectra of substrate materials uses inembodiments of an APBF laminate of the invention containing UV-blockingmeans.

FIGS. 48(A,B) show transmission spectra of additional substratematerials used in embodiments of an APBF laminate of the inventioncontaining UV-blocking means.

FIGS. 49(A,B) show transmission spectra of other substrate materialsused in embodiments of an APBF laminate of the invention containingUV-blocking means.

FIG. 50 shows an embodiment of the invention containing an edge seal forAPBF.

FIG. 51 shows an alternative embodiment of the invention containing anedge seal for APBF.

FIG. 52 schematically illustrates an embodiment of a switchable mirrorsystem employing a switchable absorptive polarizer.

FIGS. 53(A, B) show the embodiment of FIG. 52 including a TwistedNematic LC-cell (TN LC) and a Guest-Host LC-cell (GH LC). FIG. 53(A): GHLC-cell is off. FIG. 53(B): GH LC-cell is on.

FIGS. 54(A) and 54(B) show corresponding sub-sets of FIGS. 53(A) and53(B), respectively, and illustrate the principle of operation of theembodiment of FIGS. 53(A, B).

FIG. 55 schematically shows an alternative embodiment of a switchablemirror of the invention employing two switchable absorptive polarizers.

FIG. 56(A) schematically shows a front view of a segmented embodiment ofthe switchable mirror of the invention.

FIG. 56(B) illustrates multiple reflection within the plane-parallelplate;

FIGS. 57 (A-D) show embodiments of a switchable mirror employing tworeflective polarizers disposed within a TN LC-cell of the embodiment.FIG. 57(A): general structure; FIG. 57(B): both reflective polarizersare APBF-based; FIG. 57(C): both reflective polarizers are wire-gridpolarizers; FIG. 57(D): one reflective polarizer is ABPF-based andanother is a wire-grid polarizer.

FIG. 58 illustrates an embodiment of a switchable mirror systememploying two wire-grid polarizers one of which is disposed within theTN LC-cell of the embodiment and another is disposed outside of the TNLC-cell;

FIG. 59 illustrates a concept of using flattened APBFs as substrates fora TN LC-cell of an embodiment of a switchable mirror according to theinvention.

FIG. 60 shows an embodiment of the switchable mirror system with areduced number of substrates.

FIGS. 61 (A, B) illustrate two alternative implementations of a rearviewassembly employing means for recirculating light that illuminates thedisplay of the assembly and a switchable mirror system according to anembodiment of the invention.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS Definitions

As used in this description and the accompanying claims, the followingterms shall have the meanings indicated, unless the context requiresotherwise:

A “laminate” refers generally to a compound material fabricated throughthe union of two or more components, while a term “lamination” refers toa process of fabricating such a material. Within the meaning of the term“laminate,” the individual components may share a material composition,or not, and may undergo distinct forms of processing such as directionalstretching, embossing, or coating. Examples of laminates using differentmaterials include the application of a plastic film to a supportingmaterial such as glass, or sealing a plastic layer between twosupporting layers, where the supporting layers may include glass,plastic, or any other suitable material.

An “image-forming” or “image-preserving” reflector is a reflectorforming an essentially undistorted image in specularly reflected light.In imaging, optical distortion is understood as a deviation fromrectilinear projection. For example, an undistorted image of a straightline formed in a flat reflector is a straight line. For the purposes ofthis invention, “image-forming” and “image-preserving” includeprojections that may incorporate pre-determined distortions introducedby design into an otherwise undistorted image. For example, animage-forming reflector designed to be non-flat (such as a convex or anaspheric reflector) produces substantially no deviations from thecurvilinear image resulting from the design curvature of the reflector.

“Transflective” refers to an optical configuration that reflects atleast a portion of light incident from at least one side, and transmitsat least a portion of light incident from at least one side.

An “isolated defect” in an optical element is defined as a deformationfeature that may be surrounded with a complete annulus within whichthere is no excursion from the mean figure of the surface perceptible toan ordinary user. Such highly localized defects, moreover, arecharacterized by high spatial frequency when described in a Fourierdomain. For example, a particle of dust trapped within a laminate mightform an isolated defect, in which case this deformation is limited tothe region encompassing and surrounding a dust particle. Another exampleof an isolated defect in a laminate may be provided by a laminationinterface singularity (i.e., a singularity at an interface between thelaminated components) such as a scratch. Isolated defects are sometimesdefined by the rate of change in the local slope of a surface measuredwith a deflectometry-based technique developed by an automotiveconsortium and discussed by Fernholtz et al. atwww.speautomotive.com/SPEA_CD/SPEA2007/pdf/d/enabling_part1_paper4_femholz_ford.pdf.

By way of distinction, however, the terms “extended defect” and“extended distortion” refer to a deformation of the surface of anoptical element, such that there exists no complete annulus, surroundingthe deformation, which annulus contains imperceptible excursion from themean figure of the surface. An extended defect in an optical element mayinclude such features as singular elongated scratches, creases and thelike as well as groups of similar defects. Extended distortion in areflecting surface may manifest itself by and be recognized through ameasured rate of change of curvature of the surface, or, equivalently, alocal change in optical power of the reflecting surface.

An optical element is said to be “substantially devoid of extendeddistortions” if the element, in its intended use, is substantially freeof extended distortions as visually perceived by an ordinary observer.For example, an image-preserving reflector including a laminate, whichhas extended distortions that reduce the quality of the image formed bythe reflector and that can be visually perceived by an ordinary viewer,is not “substantially devoid of extended distortion.” A stippled surfacereferred to as “orange-peel” provides an example of surface havingextended distortion. Visual requirements for automotive image-formingreflectors, including rearview mirror assemblies and those with back-updisplays, are based on the intended use where images of relativelydistant objects, viewed in reflection, are moving across the field ofview of the reflectors in a generally horizontal direction when thevehicles is in motion. Therefore, a reflector producing an acceptableimage for a closer and stationary object (such as a decorative roommirror, for example), may not yield an acceptable image for anautomotive application. Verification of whether variouslaminate-containing automotive image-forming reflector assemblies formimages that satisfy the visual requirements may be carried out withdifferent tests such as, for example, a test for visual distortionevaluation of a flat mirror as described in the DaimlerChryslerCorporation standard no. MS-3612 (referred to hereinafter as visualevaluation test). If, as required by this standard, an ordinary observerlocated at about 36 inches away from the reflector, does not seeblurring or fuzziness in the image of a 1 inch grid, consisting ofintersecting straight horizontal and vertical lines and placed at about15 ft in front of the planar reflector, such reflector will be perceivedas substantially devoid of extended distortions in its intended use.When performing a visual evaluation test, the observer will often movehis head relative to the mirror to assure that a slightly discernibledistortion of the image of the grid does not become objectionable forthe purposes of the mirror use. Such dynamic evaluation is not requiredby the MS-3612 standard. It is understood, however, that other standardsmay be applied in determining the fitness of the image-preservingautomotive reflector for its intended purpose.

A “first polarization” and a “second polarization opposite the firstpolarization” generally refer to two different polarizations. In aparticular case, the first and the second polarizations may beorthogonal polarizations (such as two linear polarizations representedby mutually perpendicular vectors, or left and right circular orelliptical polarizations).

A “light source” generally refers to a device serving as a source ofillumination inclusive of optical elements that may gate or shape theillumination. Thus, for example, an LCD or any other display illuminatedwith the light from a light emitter is included within the meaning of a“light source”. A light source may be used, e.g., for display ofinformation, video images, or for illumination of an object.

A “stand-alone” element of a mirror assembly is an element that, uponbeing fabricated, does not include any elements of the mirror assemblythat serve purposes other than the purpose of the stand-alone element.No component of a stand-alone laminate of the mirror assembly may be astructural element of any other subset of the mirror assembly. Astand-alone laminate, when fabricated, can be inserted into the mirrorassembly and removed from it without disturbing the performance of theremaining elements of the assembly. In comparison, a laminate mayintegrate another element of the mirror assembly: e.g., a substrate fora mirror component may be simultaneously utilized as a substrate for thelaminate, thus becoming one of the compound material components of thelaminate.

In reference to an optical component, being “opaque” implies havingtransmittance low enough to substantially conceal mirror assemblycomponents located behind the optical component. “Opacification”, inturn, refers to an act or process of rendering an optical componentsubstantially opaque.

A “depolarizer” is an optical structure that effectively changes a stateof polarization of polarized light transmitted or reflected by thedepolarizer into a different polarization state such that differencesbetween the fundamental polarization components of incident polarizedlight are reduced after passing through or reflecting from saidpolarizer. One example of a depolarizer for present purposes would be anideal depolarizer that scrambles the polarization of light and outputsrandomly polarized light whatever the input. A practical depolarizer ofthis type typically produces pseudo-random output polarization. Forexample, an element that randomizes the phase difference between the sand p components of incident linearly polarized light passing throughsuch element provides one example of a depolarizer. Another example of adepolarizer for present purposes would be a phase retarder convertinglinearly polarized light into elliptically polarized light such as,e.g., light polarized circularly, or into randomly polarized light. Theaddition of a depolarizer to the mirror assembly may result in a moreuniform distribution of intensity with a tilt angle in both reflectanceand transmittance when a viewer wears polarizing sunglasses. Inaddition, the presence of such depolarizer minimizes certain artifactsthat appear in reflected and transmitted images.

The following disclosure describes embodiments of the invention withreference to the corresponding drawings, in which like numbers representthe same or similar elements wherever possible. In the drawings, thedepicted structural elements are not to scale and certain components areenlarged relative to the other components for purposes of emphasis andunderstanding. References throughout this specification to “oneembodiment,” “an embodiment,” or similar language mean that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the presentinvention. Thus, appearances of the phrases “in one embodiment,” “in anembodiment,” and similar language throughout this specification may, butdo not necessarily, all refer to the same embodiment.

The described features, structures, or characteristics of the inventionmay be combined in any suitable manner in one or more embodiments. Forexample, to simplify a particular drawing of an electro-optical deviceof the invention not all thin-film coatings, electricalinterconnections, elements of structural support (such as housing, forexample), or auxiliary devices (such as sensors, for example) may beshown in a single drawing. It is understood, however, that suchcoatings, interconnections, structural support elements, or auxiliarydevices are implied as they may be required for proper operation of theparticular embodiment. In the following description, numerous specificdetails are recited to provide a thorough understanding of embodimentsof the invention. One skilled in the relevant art will recognize,however, that the invention may be practiced without one or more of thespecific details, or with other methods, components, or materials.

Types of rearview mirror assemblies that contain a display and to whichembodiments of the present invention may advantageously be appliedinclude, without limitation, mirrors comprising transflective elements(i.e. elements that are partially transmissive and partiallyreflective), reflective elements including prismatic reflectiveelements, and electrochromic mirrors. Transflective optics may be,without limitation, partially transmissive, multichroic,polarization-sensitive, or directionally transmissive. Various rearviewmirror structures and related methods of fabrication have beenaddressed, for example, in U.S. Pat. Nos. 5,818,625, 6,166,848,6,356,376, 6,700,692, 7,009,751, 7,042,616, 7,221,363, 7,502,156 andU.S. Patent Publication No. 2008/0068520, 2008/0030836, and2008/0302657, and U.S. patent application Ser. No. 12/570,585 filed onSep. 30, 2009 and Ser. No. 12/367,143, filed on Feb. 6, 2009, each ofwhich is incorporated herein in its entirety by reference in itsentirety. These patent documents are collectively referred to herein as“Our Prior Applications.” Displays and transflective optics may beincorporated in various vehicle locations, not only in rearview mirrors(interior or exterior to the vehicle) and sideview mirrors, such as sunvisors, instrument panels, dashboards, overhead consoles and the like.The rearview mirror assemblies may comprise surfaces of variousgeometries such as, by way of non-limiting example, planar, cylindrical,convex, aspheric, prismatic, other complex surfaces, or combinationsthereof. As schematically illustrated in FIG. 18 in side view, anembodiment 1800 of a typical automotive rearview mirror assemblycomprises a housing 1810 with a mirror system or assembly 1815 thatincludes a mirror element or subassembly 1820 and optional auxiliaryoptics 1830 such as, e.g., various filters affecting optical parametersof light. The mirror element 1820 may include an electrochromic elementor, e.g., a prismatic element. The mirror system 1815 is often used inconjunction with an electronic device 1840, e.g., a light source thatmay include a display 1850 such as an LCD, the light L from which may bedelivered through the mirror system 1815 towards a viewer 115 to producea displayed image visible to the viewer. The light source 1840 may bedisposed within the housing 1810 as a stand-alone component behind themirror system 1815 as viewed by the viewer 115. Alternatively, the lightsource may be in physical contact (not shown) with the mirror system.Quite often contrast of a displayed image, perceived by the driver 115through the mirror system 1815 against a reflection, by the mirrorsystem of ambient light I may remain quite low, particularly when theambient light I is plentiful. In some embodiments, the electronic device1840 may be a light-detecting optical component for receiving lightthrough the mirror system 1815.

Embodiments of the invention may be incorporated in a rearview mirrorassembly that may include a glare light sensor and an ambient lightsensor, which are described in commonly assigned U.S. Pat. Nos.6,359,274 and 6,402,328. The disclosure of each of these patents isincorporated herein by reference in its entirety. The electrical outputsignal from either or both of these sensors may be used as inputs to acontroller on a circuit board of the assembly that controls theintensity of display backlighting. The details of various controlcircuits for use herewith are described in commonly assigned U.S. Pat.Nos. 5,956,012; 6,084,700; 6,222,177; 6,224,716; 6,247,819; 6,249,369;6,392,783; and 6,402,328, the disclosures of which are incorporated intheir entireties herein by reference. These systems may be integrated,at least in part, in a common control with information displays and/ormay share components with the information displays. In addition, thestatus of these systems and/or the devices controlled thereby may bedisplayed on the associated information displays.

As schematically shown in examples of FIGS. 26 and 27, a mirror assembly2600 includes a housing 2610 and, optionally, a bezel 2612 that define acavity 2714, and further includes an electrochromic mirror subassembly2616 supported in the cavity 2314 along with a printed circuit board2716. The printed circuit board 2716 has a circuit thereon that isconfigured to operate the electrochromic mirror subassembly 2616 forcontrolled darkening to reduce glare in the mirror assembly 2600. FIG.28 shows, in side view, another embodiment 2800 of a mirror assemblyincorporating the mirror element of the invention and a display. Otherexamples of mirror assemblies that may include embodiments of thepresent invention are disclosed, e.g., in commonly-assigned patentapplication Ser. Nos. 11/684,336; 12/193,426; 12/189,853; and12/196,476, the disclosure of each of which is incorporated herein byreference in its entirety.

Generally, a mirror assembly incorporating embodiments of the inventionmay include, within the housing of the assembly, an EC-mirror element ora prismatic tilt mirror element, a light source such as that includingan information display behind the mirror element, and various auxiliarycomponents such as a voice activated system, a microphone, a compasssystem, a digital sound processing system, a telemetry system, a sensorsuch as a moisture sensor or a light sensor, for example, a loransystem, a GPS, a vehicle vision system, and camera, a climate controlsystem, a turn signal, a security system, an adaptive cruise controlsystem, garage door openers, BlueTooth modules and map lights. Detaileddescription of embodiments of mirror elements and system configuredwithin automotive rearview mirror assemblies is provided in Our PriorApplications.

In further reference to FIG. 18, a reflective polarizer (RP) may provideone class of possible solutions to the recognized problem oftransmitting a sufficient and optimized amount of light from a displaythrough the mirror system to the driver. A reflective polarizersubstantially transmits light having one type of polarization whilesubstantially reflecting light of the opposite polarization. This mayproduce an effect of making the mirror system essentially transparent tothe polarized light L, generated by the light source 1840, whilemaintaining a useful level of overall reflectance of unpolarized ambientlight I incident upon the mirror system 1815. An RP might be a linearpolarizer, an elliptical polarizer or a circular polarizer and mightinclude an optical retarder such as a quarter-wave plate or a half-waveplate. A wire-grid polarizer provides one example of an RP.Alternatively, a reflective polarizer may include a polymer-based filmstructure comprising at least one optically anisotropic layer. Suchpolymer-based film structure is generally referred to herein as ananisotropic polymer-based film (APBF). In reference to FIG. 18, an APBFmay be incorporated within the mirror system 1815 by laminating the APBFto one of the components of the mirror system such as a glass substrate,for example. Alternatively, the RP may be used as an addition to thefront polarizer component (exit polarizer) of an LCD 1850 positionedbehind the mirror system 1815. The RP may also be used as a replacementfor the front polarizer of the LCD. When the viewer 115 wears polarizingglasses, it may be desirable to orient various polarizers within theembodiment 1800 of an automotive rearview mirror assembly so as tooptimize the relative intensities of the displayed and reflected imagesvisible to the viewer.

For example, some automotive industry standards require only about 40percent reflectance for inside rearview mirror assemblies and about 35percent reflectance for outside rearview mirror assemblies. With the useof such mirror assemblies, the contrast of the illumination from adisplay, as perceived by the driver through a mirror system against abackground of ambient light reflected by the mirror system, remainsquite low, particularly when the ambient light is plentiful such as on abright sunny day. For example, a commonly-assigned U.S. patentapplication Ser. No. 12/370,909 filed Feb. 13, 2009 and now published asU.S. 2009/0207513, which is further referred to herein as “Multi-ZoneMirror Application” and the entire disclosure of which is incorporatedherein by reference, provides a discussion of the display contrast in amulti-zone mirror system having both opaque and transflective areas. Thecontrast is defined as the ratio of the intensity of display-generatedlight reaching the viewer and the intensity of ambient light reflectedby the mirror system. As shown in Table 1 below, for a mirror systemhaving a transflective area with absorbance of about 10% and an assumed4,000 cd/m² raw display signal luminance and 1,000 cd/m² ambient lightluminance, the contrast of the display increases rapidly as thereflectance of the transflective area of the mirror system decreases.Embodiments of the present invention, used in rearview mirror assembliesincluding a display device, may provide for the display contrast that isgreater than 1, preferably greater than 2, more preferably greater than3, and most preferably greater than 4. The use of laminates comprisingpolymer-based films (such as an APBF) or other reflective polarizers inautomotive rearview mirror assemblies may facilitate transmitting anoptimized amount of light from the light source through the mirrorassembly to the driver. For example, by aligning the polarization axisof the APBF with the polarization vector of generally linearly polarizedlight delivered from a typical LCD located behind the mirror system, thelosses of light from the display upon passing through the APBF may beminimized. Consequently, the overall amount of light transmitted fromthe display through the mirror towards the driver tends to be increased.Teachings of such a concept employing an optically anisotropic polarizer(whether a conventional wire-grid or a laminated foil made of multiplelayers of plastic film at least one of which is optically anisotropic,e.g. wherein some or all of the film layers have internal molecularorientation that induces a directional difference in refractive index)are presented in U.S. Pat. No. 7,502,156. For example, a wire-gridpolarizer, oriented within the mirror assembly so as to transmit asubstantial majority of the linearly polarized light generated by a TFTLCD display located behind the mirror assembly, would reflect up toabout a half of unpolarized ambient light incident upon the front of themirror assembly and, therefore, provide for high visual contrast of thedisplay on the ambient background. Examples of use of reflectivepolarizers in mirror/display devices are discussed in WO 2005/050267, WO2005/024500, and WO 2003/079318, each of which is incorporated herein byreference in its entirety.

TABLE 1 Luminance of signal Luminance of reflected Contrast % T % R fromdisplay, cd/m² ambient light, cd/m² Ratio 10 80 400 800 0.5 20 70 800700 1.1 30 60 1200 600 2.0 40 50 1600 500 3.2 50 40 2000 400 5.0 60 302400 300 8.0 70 20 2800 200 14.0 95 50 3800 500 7.6

Various APBFs so far have been employed in energy efficient displayssuch as computer displays. Non-limiting examples of APBFs are providedby a multilayered polymer film comprising a body of alternating layersof a crystalline-based polymer and another selected polymer, or bymicro-structured film-based polarizers such as brightness enhancementfilms, or by dual brightness enhancement films (DBEF-E, and DBEF-Q, APF25, APF 35, APF 50, for example), all by 3M, Inc. (see, e.g., WO95/17303, U.S. Pat. No. 5,422,756), or by multilayered films containingalternating polymeric layers stretched in chosen directions. See SteveJurichich, Summary of The TFT LCD Material Report(www.displaysearch.com/products/samples/execsummary-materials.pdf); seealso 3M product description at http://solutions9.3m.com/wps/portal/3M/en_US/Vikuiti1/BrandProducts/main/energyefficiency.

Fabrication of laminates comprising glass and polymer films has beenpreviously directed to safety glazing (see, e.g., U.S. Pat. Nos.3,471,356 and 4,277,299) and to windows that reject a portion of solarlight (so-called heat mirrors, see, e.g., U.S. Pat. Nos. 6,797,396 and7,215,473). The use of polarizing films for enhancement of reflectivityin a conventional viewing mirror was discussed, e.g., in U.S. PatentApplication No. 2007/0041096 and U.S. Pat. No. 7,551,354. However,fabrication of laminates containing plastic films for employment inrearview automotive mirror assemblies has not been addressed andpresents problems that significantly differ from those faced in thefabrication of the abovementioned conventional products. The differencesstem from the performance requirements imposed upon image-formingproperties of rearview automotive mirror assemblies by commonly acceptedindustry standards.

For example, a polymer film laminated between a glass substrate and aglass superstrate for use in safety glazing is generally not required topossess any special optical or mechanical properties other than meetingtransmission standards in visible light (i.e., at wavelengths betweenapproximately 380 nm and 750 nm). A typical safety-glazing laminate isused in transmission, and the index matching provided by such polymerfilm for the glass substrate and superstrate is known to facilitatevisual concealment of imperfections present at glass surfaces. Incontradistinction, in a case of a plastic-film-based laminate withintended use in a rearview mirror assembly, where the laminate includesglass lites and a functional anisotropic polymer-based film and operatesboth in transmission and reflection, the use of an additionalindex-matching layer may not necessarily conceal imperfections. On onehand, such index-matching layer added to the polymer film will affectoptical properties of the overall mirror system (e.g., reflectance,transmittance, and image-preserving properties such as ability to formundistorted images satisfying stringent standards of automotiveindustry). On the other hand, while possibly concealing the structuraldefects of glass surfaces, the index-matching layer may not necessarilyconceal the structural defects of the polymer film itself or defects ofthe lamination. Moreover, plastic film-based laminates used in safetyglazing do not utilize structurally anisotropic and often multilayeredfilms such as those employed in embodiments of the present inventionbut, instead, conventionally utilizes homogeneous films the materialproperties of which are uniform. Therefore, technical approachessuitable to safety glass manufacture are not applicable to solve theproblems of automotive mirror design.

Methods of conventional lamination of glasses and polymer films and theresulting laminates used in conventional applications mentioned aboveare well known. For example, typical flaws of a safety-glazing laminatemay involve occasional inclusions of contaminating material such asparticulates with dimensions on the order of a few microns that aresporadically scattered across, and embedded in, the safety-glazinglaminate and may be perceived by a naked eye as annoying visual defectsof the laminate. See U.S. Pat. No. 5,631,089. These flaws are examplesof isolated defects characterized by high spatial frequency that do notreduce the integrity and quality of the laminate for its intended use insafety glazing. As far as safety glazing applications are concerned,prior art does not consider low-spatial-frequency optical distortions,resulting from the lamination process, to be defects of the laminates.See, e.g., Laminated Glass Product Standards, atwww.viracon.com/laminatedStandards.html. Similarly, plastic filmscontained within heat-mirror laminates may not perfectly conform to thecurvatures of the underlying window glass and may form wrinkles, pleatsand even cracks in the functional layer. Although structural defects oflaminates used in heat-mirrors often lead to optical defects asdiscussed, e.g., in U.S. Pat. Nos. 7,215,473 and 6,797,396, each ofwhich is incorporated herein in its entirety by reference or atwww.cardinalcorp.com/data/tsb/lg/LG02_05-08.pdf, these laminate defectsare also known to not reduce the quality of the heat-mirror laminatesfor their intended use.

In contradistinction, structural defects in laminates used in anautomotive rearview mirror may significantly reduce the quality of suchmirror for its intended use. In fact, reflective polarizers such asAPBFs, used either as stand-alone components or in laminatedcombinations, have not been commercialized to-date in image-formingautomotive reflectors such as rearview mirrors, where the applicationrequires image-forming quality satisfying automotive standards.Moreover, prior art specifically acknowledges the drawbacks ofAPBF-containing conventional mirrors known to-date by teaching that suchreflectors produce inhomogeneities of reflection (both in color anddirection) that result in disturbed reflected images prohibiting the useof APBFs and APBF-containing combinations of elements (such as, e.g.,laminates) in automotive applications. See, e.g., U.S. Pat. No.7,551,354. The present application addresses these well-recognizedproblems and offers embodiments of APBF-based laminates and automotiverearview mirrors containing such laminates that satisfy existingautomotive standards.

In various applications, a primary purpose of a mirror is to form aclear and undistorted image. When a mirror assembly of interest is usedas a rearview automotive mirror, and the image of the environmentsurrounding the driver is distorted, the unwanted image aberrations maydistract the driver from correctly evaluating the traffic situation. Wehave empirically found that (in contrast to known applications such assafety glazing applications, or heat mirrors, for example), aconventionally performed lamination, with or without a cover plate, ofan APBF to a substrate in a rearview mirror assembly compromises thequality of the resulting mirror for its intended use. Such reduction inimage quality arises from lamination defects that are characterized bylow spatial frequency in a Fourier domain. These defects may bedescribed, in some embodiments, as detachments of the APBF from thesubstrate, rather considerable in size (generally on the order or amillimeter or more in at least one dimension) and substantiallydistributed across the resulting laminate's field of view (FOV). Oftenthese defects visually present themselves to an ordinary viewer as“stretch marks” in the laminated film. As a result of such sizeable, lowspatial frequency blemishes within a rearview mirror, an image of thesurrounding seen by the driver is at least distorted and may besignificantly aberrated in the portions of the rearview mirror affectedby the described shortcomings in the APBF lamination.

FIG. 1 schematically illustrates an example of extended distortions inthe context of a laminate 100 fabricated using conventional methods oflamination. The laminate 100 includes a substrate 102, a plastic filmsuch as an APBF 104, and a cover plate 106 and might be intended toserve to optimize the transmission of light 108 generated by an optionaldisplay 110 through a mirror structure 112 towards the user 115. Anymirror structure 112 that incorporates a conventionally-fabricatedAPBF-laminate 100 generally has a reduced optical quality, regardless ofwhether the assembly includes the display 110 or not. Lamination defects116 adversely affect the uniformity of reflectance across the FOV of themirror structure 112.

Arrows 118 and 120 indicate light incident on a proximal, as observed bythe viewer 115, side 124 of the mirror structure 112 and that reflectedfrom the mirror structure, respectively. The mirror structure 112 (or,similarly, any other optical quality image-forming reflector) thatincludes an APBF-laminate 100, appears to have an uneven surfacecharacterized by non-uniform and irregular low-spatial frequencywaviness and extended distortions 116. An image formed in reflectionfrom such a mirror appears, in turn, to be optically distorted, and, inthe automotive context, the mirror structure 112 would be deficient inproviding the driver 115 with an image of the scene behind the vehicle.An example of a reflector creating optical distortions that areprohibitive for automotive purposes is shown in FIG. 2. As shown, gridimage 200 is observed in reflection, according to a specified visualevaluation test, by the front of a Nokia N76 phone display that containsa polymer-film based laminate. FIG. 2 demonstrates distinctive bendingof lines and image warping perceivable by an ordinary observer. Thereflector of such quality would not be acceptable for the intended useof an automotive rearview mirror, for example.

Exemplary Embodiments of a Method of the Invention.

FIGS. 3 and 7 schematically illustrate embodiments of a laminationprocess of the invention. In accordance with one embodiment of thepresent invention, processing steps are provided for the manufacture ofan image-preserving embodiment of this invention is now described withreference to FIGS. 3(A-G).

It was discovered that the ambient humidity at which the APBF is storedprior to the fabrication process and the humidity level maintainedduring the fabrication process may affect optical properties, structuralstability, and durability of the embodiments of the resulting laminates.In particular, the elevated levels of humidity during the pre-processingstorage generally led to increased haziness (and, therefore, to reducedtransmittance and increased scatter of light) in the fabricatedlaminates after the durability testing. Therefore, optionally, anembodiment of the fabrication process of the invention includes a stepof pre-lamination processing of the APBF (shown in a dashed line as step(A) in FIG. 3), during which the water content of the film is assurednot to exceed a chosen level. Characterization of haze levels wasconducted according to standards of the ASTM (American Society forTesting and Materials) and is discussed in more detail below. For aresulting laminate-containing embodiment of the invention to exhibittransmitted haze levels that are less than about 5% after thepost-fabrication testing (such as testing at 96 hours at 105° C.), theemployed APBF should preferably be stored, prior to the laminationprocess, at a temperature not exceeding about 40° C. and the relativehumidity (RH) less than 95% for less than 8 hours, or conditions thatlead to an equivalent water content change in the polymeric material.Similarly, in order to maintain haze levels below about 3% after thepost-fabrication testing, the film should preferably be stored at lessthan 40° C. and less than 95% RH for periods less than 4 hours.Similarly, to reduce transmitted haze to below about 1% after thepost-fabrication testing, the pre-processing storage temperature shouldpreferably be lower than 25° C. and at RH should be lower levels of lessthan about 30%.

Alternatively or in addition, to keep a pre-lamination moisture contentof the film within the preferred limits resulting in reduced haze of thefinal laminate, the APBF may be appropriately treated prior to thelamination process. Such treatment may include drying the APBF filmunder vacuum and elevated temperatures (approximately between 25° C. and40° C.) for at least 4 hours. It shall be appreciated that measurementsof moisture content in a given APBF can be carried out using differenttechniques. For example, a sample of DBEF-Q of a known area (e.g.,dimensioned to match the full size of the rearview mirror substrate) maybe precisely weighed and then subjected to particular storing conditionssuch as 40° C. at 95% RH, 40° C. in vacuum, or control ambientconditions (room temperature, open lab bench). The sample then may beprecisely weighed at known time intervals (e.g., 2, 4, 8 hours) todetermine the extent of weight gain or loss. The change in weight-% ofmoisture in the film is then determined from two weight measurements.The lamination processing and post-processing testing that follows allowfor correlating various optical properties, including transmitted hazelevels, of the laminate-containing embodiment of the invention with thedetermined initial levels of moisture content of the APBF. According toone embodiment of the invention it is preferred that the water contentof the APBF prior to lamination be less than about 0.6 weight-%, morepreferably less than about 0.4 weight-%, even more preferably less than0.2 weight-%, and most preferably less than about 0.1 weight-%.

During the fabrication process, an optionally pre-treated at step (A)APBF 302, which may be about 100 μm thick, is disposed, at step (B)(“Assemble a Composite”) of FIG. 3, on a surface of a substrate 304 asshown by an arrow 306. A superstrate 308 (also alternatively referred toherein as a cover plate) is then disposed over the APBF, which isindicated with an arrow 310, to form a composite 312. Although exemplaryembodiments of FIG. 3 are discussed with reference to an APBF, it shallbe understood that generally any other film may used for application tothe substrate 304 with a purpose of fabricating a laminate thatsatisfies automotive image-forming requirements, as described below.

In a specific embodiment, the substrate may be made of optical qualityglass or other materials suitable for use in an image-preservingreflector assembly and may be flat or have a selected curved shape. Theconfiguration of the superstrate 308 may be substantially the same asthat of the substrate 304, and surfaces of the substrate and superstratemay be conforming to each other. It should be realized, however, thatoverall dimensions of the substrate and superstrate are generally notrequired to be the same. In the context of rearview mirror assemblies, acomponent of the mirror system may perform as a substrate or asuperstrate for a laminate. For example, the mirror element 2220 of FIG.22 may be used as a substrate, and an additional lite of glass orappropriately chosen plastic (with optionally deposited opticalcoatings) may serve as a superstrate.

The polymer-based film 302 may be extruded or molded, or fabricatedusing other known methods, it may comprise a single layer (such as alayer of a low-density polyethylene, see, e.g., U.S. Pat. No. 5,631,089)or be a multi-layer film stack (such as a stack of alternating layershaving high- and low refractive indices) some of the layers of which maybe optically anisotropic (e.g., birefringent). For example, the film 302may contain commercially available plastics such as acrylics,polycarbonates, silicone, polyester, polysulfone, polycyclic olefin,PVC, or the like having nominal indices of refraction from about 1.3 toabout 1.8. The stack of layers with alternating refractive indices maybe used to enhance the reflectance of light having a given polarizationwhile simultaneously optimizing the transmittance of light havinganother polarization state. Such anisotropic layers may include, in oneembodiment, a prismatically microstructured surface similar to thatdisclosed in U.S. Pat. No. 5,422,756 that facilitates the separation ofthe incident light into two components having orthogonal polarizations.In addition or alternatively, the film 302 may comprise a plurality ofalternating polymeric layers of at least two types having, respectively,high and low refractive indices at one polarization and different highand low refractive indices at an orthogonal polarization. One example ofsuch film, comprising alternating layers of crystalline naphthalenedicarboxylic acid polyester, was described in WO 95/17303. In yetanother alternative embodiment, the multilayer polymer film 302 maycomprise a layer that has a spatially oriented structure realized, forexample, by stretching an otherwise isotropic polymer film in a chosendirection.

It should be noted that, to assure adequate flattening of the film 302between the plates 304 and 308 at the step (B) of FIG. 3, the film maybe optionally put under tension. For example, the film 302 may beuniformly stretched in radial directions at about 0.1 oz. to about 60lbs per linear inch. In some embodiments, the preferred tension may bebetween about 1 and about 10 lbs per linear inch. In one embodiment, theinitial application of the optionally stretched polymer-based film 302onto the substrate can be complimented with using a soft press roll at anip pressure of about 5 to 500 psi to assure that the film 302 conformsto the surface of the substrate 304.

During the “Laminate/Bond” step (C) of FIG. 3, heat, pressure, andoptionally vacuum are applied to the composite 312. In general, thecomposite may be vacuum-bagged, evacuated, and autoclaved under pressurefor time sufficient to bond the film 302 to at least the substrate 304without forming spatially extended lamination defects described aboveand to form a substantially image-preserving laminated opticalcomponent. It was unexpectedly discovered that application of pressureto the surface of the composite at elevated temperatures, as discussedin the literature, may not be adequate for ironing out the imperfectionsand wrinkles from the film 302 for the purpose of producing a laminatepossessing optical qualities that satisfy automotive industry standards.One possible solution to this problem is to apply substantiallyomnidirectional pressure (such as that attained in a pressure autoclave)to the laminate composite. Processing parameters and the resultinglaminates are further discussed below. Following the application of heatand substantially omnidirectional pressure, the laminate is formed. Inthe embodiment 314 of the laminate of FIG. 3(D), for example, thepolymer film 302 is shown to have adhered to both the substrate 304 andthe superstrate 308. In a specific embodiment, no adhesive is usedbetween the layers 302, 304, and 308 of the composite 312 during thelamination procedure. Although the presence of adhesive along a surfacewithin the laminate structure does not change the principle of themethod of the invention or the resultant construct/assembly, it wasunexpectedly found that laminates formed with substantially no adhesivealong at least one lamination interface between the plastic film and thecover plates tend to have higher probability of producingimage-preserving rearview mirror assemblies of optical quality definedby automotive standards.

In a related embodiment, a superstrate portion 308 of the laminate maybe removed, as shown at an optional step (E), “Release Superstrate”, forexample after the lamination has been complete but prior to the qualityinspection step of the process of the invention. As shown in FIG. 3(F),the polymer-based portion 302 of the laminate 316, which resulted aftera superstrate release, has an exposed surface 317. To facilitate arelease of the superstrate 308 at the “Release Superstrate” step (E) ofFIG. 3, the superstrate may be appropriately treated, prior to the“Assemble Composite” step (B) of FIG. 3, according to any method knownin the art to prevent it from being permanently adhered with the filmstructure 302. For example, in reference to FIG. 3(A), a suitable filmor coating (also referred to as a release layer) may be applied to theinner surface 318 of the superstrate 308 facilitating the removal of thesuperstrate and allowing for the APBF 302 to remain attached to thesubstrate 304. Alternatively, the inner surface 318 may be treated witha release-facilitating chemical agent such as, e.g., an alkylsilane, orany of the commercially available silicone or wax-based release agents.It has been discovered that these various release agents do notfacilitate formation of visibly perceivable defects in the laminate anddo not appreciably impede transmission of light through the laminate. Inaddition or alternatively, the surface 317 of the polymer-based film 302may be similarly treated prior to the assembly of the composite. As aresult, the superstrate 308 is releasably adhered to the film 302 andcan be easily removed either manually or automatically.

To enhance adhesion of the DBEF or other APBF to a desired substrate orsuperstrate and to improve durability of the resulting laminate, thesubstrate and/or the superstrate is preferably cleaned (not shown)before the lamination process to remove contaminants which couldinterfere with adhesion and induce optical defects. Cleaning can beaccomplished chemically using detergents, solvents, or etchants toremove gross contamination. In addition or alternatively, mechanicalcleaning of a substrate may be employed using polishing compounds suchas aluminum oxide or cerium oxide can be used to further prepare thesubstrate surface. In addition, at least one of the substrates and thepolarizing film can be optionally pretreated (not shown) to enhanceadhesion. Surface treatment such as with flame, ozone, corona plasma, oratmospheric plasma can be used to further clean and/or functionalize thesurfaces to be bonded. Adhesion promoters or coupling agents such asorganofunctional silanes, organotitanates, organozirconates,zircoaluminates, alkyl phosphates, metal organics or adhesion-promotingpolymers can be deposited in a thin-film form using a variety oftechniques. These promoters and coupling agents are used to bridge theinterface between the inorganic and organic substrates and improveoverall adhesion and resistance to humid environments. Examples ofsuitable adhesion promoters include Z-6011 silane (from Dow Corning) andSilquest A-1120 silane (from G.E. Silicones).

It shall be also understood that in an embodiment where the superstrateis removed (or released) and thus does not remain part of the laminate,the superstrate generally does not have to be made of a transparentmaterial. In such embodiment, various superstrate materials can besuitably used such as, e.g., ceramics, metals, carbide, boron-nitride,fluorocarbon, phenolic, acetal or nylon. Moreover, in such embodiment,at the initial steps of fabrication of a laminate, the use of asuperstrate 308 may not be required at all.

FIG. 7 illustrates some alternative embodiments pertaining tointermediate steps of fabrication of a laminate with and without asuperstrate. As shown in FIG. 7(A), for example, an arm 702 of apressing mechanism may be made of a material suitable for release fromthe polymer portion 302 of the laminate and is withdrawn after thebonding step of the process. Therefore, the arm 702 itself may performas a superstrate 308 releasable from the laminate 316 of FIG. 3(E)during the laminate fabrication cycle. In comparison, as shown in FIG.7(B), a superstrate 308 may be initially attached to the arm 702 andremain a bonded part of laminate 314, prior to being released. FIG. 7(C)illustrates fabrication of the embodiment of the laminate using apress-roll 704. As was mentioned above, in some embodiments, to assurethat the quality of the laminate satisfies the imposed image-preservingrequirements, applying omnidirectional pressure may be preferred toapplying pressure otherwise. The lamination of the DBEF in an autoclavehas been shown to assure processing conditions adequate to modify theoptical quality of the DBEF for use as a high quality specularimage-preserving reflector. The DBEF or other APBF itself can beoptionally pre-processed prior to attachment to the mirror element. Aweb method for pre-processing the APBF for higher optical quality is topass the APBF compressed between one or more pairs of rollers that maybe optionally heated. This optional treatment facilitates flattening ofthe film and may be used in addition or as an alternative to stretchingthe film, as discussed above. The flattened APBF can then be laminated.

(1) Heat-Press Operation:

An APBF-including composite (such as, e.g., the composite 312 of FIG.3(B)) may be initially placed cold in a press and then heated undersubstantially omnidirectional pressure to a final processingtemperature, in accordance with step (C) of FIG. 3. Generally, theapplied pressure may be varied based on the processing temperature. Byway of example, one embodiment may include a two-step processing, when acomposite that is kept at some predetermined initial pressure may beheated to a preferred processing temperature at the first step. At thesecond step, once the preferred processing temperature has been reachedand maintained, the pressure is ramped up as a chosen function of time.Alternatively, at the first step, the pressure applied to the compositemay be ramped up as a chose function of time at a constant level oftemperature, and then, at the second step, the temperature may be rampedup to a preferred operational level while the level of pressure ismaintained. Alternatively, the composite may be first preheated to afraction of the final processing temperature, then appropriately pressedand heated further to the final temperature. Various other options ofchanging temperature and/or pressure with time, simultaneously orseparately, are contemplated as embodiments of the present invention.Optionally, the cover plates 304 and 308 and the APBF 302 may be firsteach preheated to some fraction of the final processing temperature,then assembled with an APBF into the composite 312, which is furtherexposed to pressure and heated to the final processing temperature.Optionally, the cover plates 304 and 308 and the APBF 302 may be heatedto final processing temperature, then assembled into the composite andfurther exposed to the required pressure. If a press is used, the pressanvil(s) may be flat or profiled and made of a compliant material anddesigned to apply force as required. In one example, a composite 312 ofFIG. 3(B) was laminated with the use of a hydraulic press equipped witha heated bottom plate and a top plate having a silicone bladder. Thebottom plate of the hydraulic press was preheated to 95° C. using a heatexchanger and re-circulated heat transfer fluid. Following the placementof the cold composite into the press cold and application ofapproximately 130 psi of pressure (as measured at the bladder, orapproximately 1800 psi at the hydraulic ram), the composite was allowedto age 30 to 60 minutes. Samples produced in this manner exhibitedacceptable optical properties and met durability requirements asdescribed below.

(2) Oven/Roller System:

The composite such as composite 312 of FIG. 3(B) may be placed in a coldoven, heated to the final processing temperature, and pressed in atleast one roller press. Alternatively, at least one of the cover plates304 and 308 may be preheated to a fraction of the final temperature,following which the composite with the APBF is assembled, then pressedin at least one roller press and heated to the final processingtemperature. Optionally, the components of the composite may be heatedto the final processing temperature, assembled into the composite, andthe roll-pressed. Press rollers used may be flat or profiled to applyforce as required.

(3) Sonic Heat Press and Inductive Heat Press provide alternativefabrication approaches. For example, heating at least one of the coverplates 304 and 308 and the film 302 during the lamination process may beaccomplished ultrasonically. A sacrificial film (e.g., a film disposedbetween the APBF and an anvil in the embodiment of FIG. 7(B)) may beused to preserve the cosmetics or functionality of the APBF. Heating mayalso be accomplished inductively using the transparent conductive oxide(TCO) or metal films that are adjacent to the APBF and operate as theheating element to attain at least a fraction of the final processingtemperature. For example, the components to be laminated may beconventionally preheated to some portion of the final temperature, thenpressed and inductively heated. The inductive heating and pressing maybe advantageous in allowing for selective sealing of the APBF tosubstrates that have conductive properties. The press anvil(s) used maybe flat or profiled to apply force as required.

(4) RF-Lamination Press:

Radio frequency (RF) lamination technology, such as FastFuse™ RF GlassLamination Technology available from Ceralink Inc. (Troy, N.Y.),combines high-speed RF-heating with pressure to produce laminates andmay be advantageously used to produce glass/plastic film laminates withpotential time and energy savings. In practice, an APBF-includingcomposite such as the composite 312 of FIG. 3(B) may be initially placedcold in a press and then heated using RF while simultaneously applyingpressure. Specific temperature and pressure parameters of suchembodiment are discussed elsewhere in this application. Various optionsof changing temperature and/or pressure with time, simultaneously orseparately, are contemplated as embodiments of the present invention.

At a post-lamination processing step (G), shown in FIG. 3, the qualityof embodiments of a fabricated laminate (such as the laminate 314 havingan APBF sandwiched between two cladding elements or the laminate 316having the film bonded to only one cladding element) may be verifiedvisually or by using an appropriate measurement technique. For example,a wave-scan device from BYK-Gardner (see www.byk.com), such as the“wave-scan dual” may be readily adopted for measuring through thesubstrate or superstrate, the quality of the lamination interfaces.Defects in an interface formed by laminated or bonded surfaces may becharacterized based on sizes of the lamination defects, with respect toif and how these defects affect the clarity of the image obtained inreflection from such interface. In particular, the BYK-Gardnermeasurement system uses a “short wave”, or SW, designation for detecteddefect features having dimensions from about 0.1 mm to approximately 1.2mm and a “long wave”, or LW, designation for detected distortionfeatures of 1.2 mm to approximately 12 mm in size. (Characterization insmaller dimension ranges is also possible). The values SW and LW areprovided on a normalized scale from 0 to 100, where lower valuescorrespond to smaller structural distortions and waviness of thelaminated interface than higher values. Alternative metrics provided bythe same wave-scan dual approach provide quantification of surfacedistortions on a more detailed spatial scale. These metrics, Wa, Wb, Wc,Wd and We quantify surface distortions with frequencies corresponding to0.1 to 0.3 mm, 0.3 to 1.0 mm, 1 to 3 mm, 3 to 10 mm and 10 to 30 mm,respectively. Depending on the application, distortions on differentlength scales may be more or less noticeable and/or objectionable to theviewer. In the case of automotive mirror applications, surfaceundulations on the scale of less than about 3 mm are the most important,because these shorter-wavelength optical distortions are more disruptiveto perceived reflective images as compared to the longer-wavelengthdistortions. Because the W metrics are more detailed than the SW and LWmetrics, inclusion of the W readings (in particular the Wa, Wb and Wereadings) as additional or alternate metrics to quantify acceptabledistortion may lead to a more complete set of criteria for determiningacceptable distortion levels.

Using a “wave-dual scan” measurement technique and applying SW and LWmetrics, it has been empirically found that a reflector may be suitablefor most non-automotive applications if it is characterized by SW and LWvalues less than about 10, preferably less than about 7, more preferablyless and 5, and most preferably less than 3. In contradistinction,image-preserving reflectors with intended use in rearview automotivemirror assemblies (including those containing laminated interfaces)should preferably be characterized by SW and LW values that are lessthan 3, more preferably less than 2, and most preferably less than 1.The alternative use of individual Wa, Wb and We metrics indicates,however, that, in order to have a mirror system with acceptablereflective properties, at least one of these W-metrics should be lessthan 7, more preferably less than 5, and most preferably less than 3. Itis preferred, however, that more than one of these W-metrics be lessthan 7, more preferably less than 5, and most preferably less than 3. Itis understood that various other optical techniques such asinterferometric profilometry, or measuring of light scattering, or anyother known in the art approach suitable for surface characterizationmay be alternatively used to describe the quality of the laminatefabricated according to an embodiment of the method of the invention.

As yet another alternative, the quality of the APBF-based laminates andmirror structures containing such laminates can be characterized withthe use of ONDULO technology developed by Visiol Technologies (France)based on the principle of phase shifting deflectometry and commonly usedin automotive industry for evaluation of visual defects occurring whentwo panels are bonded together. The goal of this non-contactingtechnique is to quantify the structural defects in inspected reflectinginterface (whether curved or flat) based on distortions of thereflection of a fiducial object in that interface. Based on theevaluation of such distortions, the data are generated representingspatial derivatives of the slope of the surface of the reflector, and aconclusion of the type and distribution of structural defects in thatreflector is obtained. The metric used for evaluation of the opticaldistortions with this technology is defined as “Curvature Units” (CU).The advantage of using the deflectometry approach is its high spatialresolution, the ability to recognize both isolated, point defects andextended defects, and a good correlation with visual tests. We haveempirically found that image-preserving laminates with intended use inrearview automotive mirror assemblies should be characterized by CUvalues with moduli not exceeding approximately 0.04, preferably noexceeding 0.03, more preferably not exceeding 0.02, and most preferablynot exceeding 0.01. An alternative technique for quantifying medium andsmall scale defects in an embodiment of a laminate of the invention maybe based on a (local) measurement of a difference in optical powers of aflat reflecting surface and that of a flat reference surface, caused bythe presence of structural defects in the reflecting surface. See, e.g.,a description by ISRA Vision AG at www.isravision.com. In thistechnique, a set of fiducial lines is projected onto the testedreflecting surface, moved in front of the computerized line-scandetector that captures and analyzes the reflected image in comparisonwith a reference image. A conclusion about the surface defects isexpressed in units of millidiopters of optical power of the surfaceunder test. According to the embodiments of the present invention,image-preserving laminates with intended use in rearview automotivemirror assemblies and measured using ISRA approach are characterized bylocal optical power values of less than 1,000 millidiopters, morepreferably less than 750 millidiopters, even more preferably less than500 millidiopters, and most preferably less than 250 millidiopters.

The following discussion provides some examples of lamination processesand the resulting laminate structures, obtained according to theembodiments of the invention for the intended use in automotive rearviewmirror assemblies. Generally, the temperature T selected to laminate aninitial composite is within a range from about 50° C. to about 160° C.,preferably between about 80° C. to about 150° C., and most preferablybetween about 90° C. to about 110° C. The levels of substantiallyomnidirectional pressure P chosen for lamination are between about 25psi to about 2,500 psi, preferably from about 50 psi to about 500 psi,and most preferably from about 100 psi to about 400 psi. The weightcontent of water in an APBF to be laminated is maintained as discussedabove. The lamination time can generally vary between about 1 and 600minutes, preferably between 5 and 180 minutes and most preferablybetween 15 and 60 minutes. However, different processing parameters maybe used, provided that the quality of the optically active,polarization-affecting layer of the APBF is not compromised. Optimaltime, temperature, humidity, and pressure generally depend on the choiceof materials used in fabricating the APBF and particular media used inan autoclave. In some embodiments, the use of liquid in an autoclaveimproves the uniformity of temperature across the composite and improvesheat transfer.

In one embodiment, for example, a glass-plastic composite of about 55 mmby 75 mm in size was formed by sandwiching an APBF reflective polarizingfilm (from Nitto Denko corporation), having a thickness of about 2 milsand a pressure-sensitive adhesive on one of its sides between a 1.6 mmthick substrate and a 1.1 mm thick superstrate, with the film's adhesiveside facing the superstrate. The laminating process included assemblinga composite at preferred levels of water content in the film and vacuumbagging the composite, followed by autoclaving at the temperature ofabout 90° C. and a gauge pressure of about 200 psi for 1 hour. Both thevisual image testing, as described above, and the wave-scan BYK-Gardnertesting confirmed that the quality of the laminate was satisfactory forits intended purpose in the automotive rearview mirror assembly. Inparticular, the wave-scan measurement of the laminated glass-polymerinterface through the substrate produced normalized averaged surfacefigures of about SW 0.4 and LW 0.8 for the first and the seconddimensional ranges of features measured by the BYK-Gardner device. Whenan APBF has surfaces with different texture, it may be advantageous toform a laminate in such a fashion as to have this smoother side later onplaced towards the observer in the overall rearview mirror system.

In further reference to FIGS. 3(A-G), we have discovered that, in orderto facilitate a defect-free fabrication of a laminate containing thefilm 302 that is multi-layered, it may be preferred in some embodimentsto have the cladding or adjacent layers of the multilayer film 302comprise materials having different glass transition temperatures orother properties. In other words, prior to fabrication of anAPBF-containing laminate, a targeted engineering of an APBF componentmay be required to improve at least one of adhesion and opticalproperties to obtain a laminate that is substantially free of extendeddistortions and that meets the environmental requirements and therequirements on the quality of optical image. In one embodiment, theAPBF may include a three-layer or a multi-layer film structure with atleast one core optically anisotropic layer having high T_(g) (e.g.,T_(g,core)˜140° C.) that is sandwiched between two or more generallydissimilar cladding layers each of which has a corresponding different(e.g., lower, T_(g, clad)<T_(g, core)) glass transition temperature anddifferent material and mechanical properties such as hardness. Informing the laminate composite with such multi-layered APBF structure,where the cladding layers are placed in contact with components servingas a substrate and a superstrate of the composite, the laminationprocess may be advanced in several ways. First, an appropriate choice ofmaterials for cladding layers may assure that the core, anisotropiclayer of the APBF is sufficiently flat and would not be crumpled betweenthe glass plates during the lamination. In one embodiment of the presentinvention, the plastic-based cladding layers of the multi-layered APBFare chosen to possess a hardness value of at least Shore A 70, asmeasured with methods known in the prior art. In another embodiment, thehardness if at least Shore A 80 is preferred. Second, it was discoveredthat the lowest glass transition temperature (among the transitiontemperatures of the cladding layers) generally correlates with thepreferred lowest suitable lamination temperature. Therefore, in oneembodiment of the invention, during the lamination of a multi-layeredAPBF between a substrate and a superstrate such as those made of glass,the amount of heat applied to the composite of 312 of FIG. 3(B) could bedefined, for example, by a temperature exceeding the lower limit of theapplicable dynamic range of glass-transition temperatures. The optimaltemperature for laminating a composite containing a multilayered APBFwas found to be generally between a first temperature value (that isabout 10° C. below the onset of the lowest temperature within thedynamic range of glass transition temperatures) and a second temperaturevalue (that is about 10° C. higher than the highest temperature withinthe dynamic range). Multi-layered APBFs engineered for the purposes oflaminates with intended use in automotive rearview mirror assemblies maybe more complex. For example, a core, optically anisotropic layer of amultilayered APBF may itself include multiple isotropic and birefringentlayers. Optionally, one of the cladding layers of the multi-layered APBFfilm structure may be a depolarizing layer employed to depolarize aportion of the display-generated light and/or the light reflected by themirror assembly.

A major effect of adding a depolarizing component to a reflectivepolarizer in a conventional application was considered in a prior artbacklighting system, where a reflective polarizer was shown to enhancethe perceived brightness of the LCD. To achieve such enhancement, thereflective polarizing film was placed between a light emitter and an LCDin such a fashion as to align polarization of light transmitted from thelight emitter through the reflective polarizer with a direction requiredfor optimal operation of the LCD. It will be realized that the additionof a depolarizing component to such a conventional backlighting systembetween the reflective polarizer and the LCD (i.e., on the other side ofthe RP as seen from the light emitter) reduces a degree of polarizationotherwise resulting when only the reflective polarizing film is present.This situation is illustrated in FIG. 19. Indeed, in this case,polarization of light transmitted from the light emitter towards the LCDthrough a sequence of the reflective polarizer and depolarizer would besubstantially randomized, and the overall backlighting display systemwould to an extent operate as if the combination of the reflectivepolarizer and depolarizer were not placed between the light emitter andthe LCD at all. As shown, an RP 1910 is used to optimize transmission ofunpolarized light from a light emitter 1920 through an LCD 1940 in aconventional display application by re-circulating a portion of theemitted light between the RP 1910 and a reflector 1950, positioned onthe opposite sides of the light emitter 1920 in a fashion described inprior art. Here, the addition of a depolarizing component 1960 negates,to some extent, the benefit provided by the RP. In contradistinctionwith conventional applications such as the above-described backlightingapplication, the use of a combination of the RP and depolarizer in oneembodiment of the invention provides certain advantages, as discussedbelow. Specifically, the resulting embodiment of a rearview mirror isnot only characterized by optimized transmittance of light from thelight source through the mirror system but it also performs in a fashionsubstantially unaffected by angle effects otherwise typically noticed byan image observer (such as a driver) wearing polarized glasses.

In a specific embodiment of the invention, at least one of the substrateand superstrate of the laminate may be made of plastic. The resultinglaminate may be used, e.g., as a stand-alone component within the mirrorsystem to provide an image-preserving rearview mirror satisfying theautomotive standards. In this embodiment, plastic materials may bechosen to have corresponding glass transition temperatures exceeding theoptimal temperature used in the lamination process. Examples of suchmaterials are polycyclic olefin, polycarbonate, acrylic, polyimide,polyether-sulfone or epoxy. It shall be understood, however, that anyother material suitable for use, in an image preserving reflector, as asubstrate or a superstrate for a polymer-based film laminate can beused. In an embodiment where a superstrate of the laminate is notreleased, a component of the mirror system performing the role of thesuperstrate and positioned between the display and the reflectivepolarizer should preferably be formatted to not substantially depolarizelight.

Once the lamination interface has been formed, it may be optionallyprotected (not shown in FIG. 3) from oxygen, water, or othercontaminants by having the edge of the laminate sealed. If necessary,the film may be cut slightly smaller than the substrate and superstratethus providing a notch therebetween for the sealing material to reside.Sealing may be accomplished with a variety of crosslinked materials suchas moisture cured materials, thermoset or UV cured materials, preferablywith materials having low curing temperatures. Silicones, epoxies,acrylates, urethanes, polysulfides provide but a few examples of suchmaterials. Additionally, thermoplastic materials such as warm or hotmelt polyamides, polyurethanes, polyolefins, butyl rubber,polyisobutylene and the like may be used for the purpose of sealing thelaminate. Examples of suitable sealing materials include LP651/655 (fromDELO, Germany) and the Eccoseal series of sealants (from Emerson &Cuming).

Exemplary Embodiments Utilizing a Prismatic Element or an EC-Element.

Embodiments of laminar structures provided by the process of theinvention (e.g., the embodiments 314 and 316 of FIGS. 3(D) and 3(F),respectively) are useful in image-preserving and image-forming reflectorassemblies such as rearview automotive mirrors, which form imagessubstantially free of extended distortions because of the quality of theemployed laminar structures. For example, as shown in an embodiment 400of an electrochromic dimmable mirror assembly of FIG. 4(A), the APBF 302is laminated to the embodiment 402 of an electrochromic element(discussed with reference to FIG. 7 of the commonly-assigned U.S. Pat.No. 7,009,751, the disclosure of which is incorporated herein in itsentirety) between the rear surface 114 b of the rear element 114 of theEC-element and the light source 170, which may be a backup display. Inan alternative embodiment, however, a laminate of the invention can beadvantageously used with other types of reflecting structures. As shownin FIG. 4(B), e.g., the laminate 314 of FIG. 3(D) may be employed as astand-alone component within a non-dimming tilt prism-mirror structure404 (including a stand-alone tilt prism element 408), behind which theremay be optionally positioned an information display (not shown).Alternatively, a tilt prism element assembly 410 may incorporate an RP(APBF) element 302 that is laminated to one of the components of thetilt mirror itself, as shown in FIG. 4(C).

A) Specific Embodiments of a Switchable Mirror System Employing aLiquid-Crystal Cell and a Prismatic Mirror Element.

Furthermore, embodiments of the present invention may incorporate a“switchable” mirror system that utilizes an auxiliary LC-cell or device.Such switchable mirror system may operate at different levels ofreflectance, transmittance, or both. Although such a switchable mirrormay be configured to operate in either a high-reflectance or alow-reflectance state when the power to the LC-cell is off, it may bepreferred to configure the switchable mirror system of the presentinvention to operate in the former mode. If this configuration isachieved, the mirror system will provide for and maintain the optimalrear-vision conditions when the system fails, that is when either themirror system itself or a display behind the mirror system fails orloses power. As shown in an embodiment 420 FIG. 4(D), a liquid crystalcell or device 422 may be any LC-cell capable of modulating light (by,e.g., changing a polarization state of light through either rotation ofpolarization or absorption of light having a particular polarization).Examples of applicable LC-cells include a Twisted Nematic (TN) cell, aSuper Twisted Nematic (STN) cell, a guest host or phase-change LC deviceincorporating a dichroic dye, a Ferroelectric LC device such as asmectic ferro-electric cell, a nematic Distortion of Aligned Phases(DAP) LC device. Any of these cells or, alternatively, one or more cellscontaining cholesteric material and used with or without a quarter-waveplate as described in a commonly assigned U.S. Pat. No. 7,502,156 can beplaced in front of the RP (APBF) element 302 to modulate the ambientlight 118 incident upon the proximal side 124 of and reflected by themirror system 420 and/or light transmitted through the system 420 from alight source disposed behind the distal, with respect to the observer,side 424 of the system 420. In operation, this embodiment allows forswitching the reflectance state of the mirror system from anintermediate state (of about 35% or above) or a high state (about 70%and above) to a level of reflectance of about 4% provided by only afirst surface of the embodiment, by “flipping” the prism manually orautomatically as done in vehicles currently equipped with prismaticrearview mirror assemblies. Although the embodiments of FIGS. 4(B)through 4(D) are shown as employing a prismatic mirror element, it willbe appreciated that “switchable” mirror-system embodiments may alsoemploy an auxiliary LC-device in a combination with a dimming mirrorstructure such as one containing an EC-element. Non-limiting examples ofEC-element based embodiments of“switchable” mirror systems of theinvention are further discussed below in reference to FIGS. 33 (A, B)and 34. It should be noted that, in a practical rearview mirror system,preservation of image quality and clarity and reduction of spuriousreflections and double-imaging as viewed by the observer 115 dictatesthat a separation between any two highly reflective surfaces of thesystem be minimized. In embodiments of the invention such separationshould be reduced to less than 2.5 mm, and preferably to less than 1,and most preferably to less than 0.5.

B) Embodiments Employing a Prismatic Mirror Element.

In a specific embodiment, schematically shown in FIG. 4(E), the RP 302may be laminated directly to the LCD subassembly 1850 or some componentsof the LCD subassembly and then to the mirror element 1820 (which mayinclude a prismatic optical element or an electrochromic element) so asto optimize the number of optical interfaces present and improve theoverall reflectance and transmittance properties of the rearview mirrorsystem. In another embodiment it may be useful to include an additionallayer of PSA containing a UV-blocking agent, or a UV-blocking polymerfilm in front of an APBF, as seen by the observer. The addition of suchUV attenuating agents or blockers may prevent visual degradation of theAPBF and/or degradation of the integrity of the APBF-containinglaminate. The implementation of such UV-blocking elements in embodimentsof the invention is discussed in detail below. In embodiments where theAPBF is located behind the electro-optic cell such as an EC-element or acholesteric element, it is possible to dispose the UV-attenuating agentswithin the electro-optic cell. Cholesteric devices and EC-elementsincluding these agents are taught, respectively, in a commonly assignedU.S. Pat. No. 5,798,057 and in commonly assigned U.S. Pat. No. 5,336,448and U.S. Pat. No. 6,614,578, each of which is incorporated herein in itsentirety.

Reflecting structures and assemblies such as rearview mirrorsincorporating polymer-based films laminated according to the embodimentof the invention generally do not exhibit optical blemishes, are devoidof extended distortions, and do not produce image distortions thatdistract the viewer, as discussed above, thus preserving the quality ofoptical imaging within the requirements of automotive industrystandards. Although embodiments of the invention are discussed in thisapplication with respect to placing an APBF-containing laminate of theinvention in particular locations within a rearview mirror assembly, itwill be noted that, generally, positioning a laminate of the inventionin other suitable locations is also contemplated. In one embodiment ofthe rearview mirror, e.g., an additional APBF-containing laminate may bedisposed behind the display, as seen by the observer.

In a specific embodiment, an air gap or cavity can be formed betweensurfaces of the mirror system and later preferably sealed with aperimeter seal to avoid entrapment and/or condensation of vapors anddust. For example, a mirror assembly may include constructions such as[G/RP/air/G] or [G/RP/G/air/G/ITO/EC/ITO/G]. In these exemplaryconstructions, the components or media are listed starting with the onefarthest from the viewer, the “air” denotes a cavity or a gap that maybe defined by the perimeter seal and/or spacer disposed between theadjacent components separated from one another, “RP” refers to a layerof reflective polarizer such as APBF, for example, and “G” denotes alite of glass or other suitable substrate material. FIGS. 4(F) through4(H), schematically showing embodiments of a mirror assembly employing aprismatic mirror element, provide several non-limiting examples of suchconstruction sequences. FIG. 4(F) illustrates a prism-based embodimentthat relates to the embodiment of FIG. 4(C), but in which the prism 408is spatially separated from a laminate 316 containing the RP 302 and theglass substrate 304 by an air-filled cavity 435 formed with the use of aperimeter seal and/or spacer 438 placed between the prism 408 and the RP302. The corresponding construction sequence may be described as[G/RP/air/prism]. FIG. 4(G) provides an alternative embodiment includingthe air-gap 435, in which the laminate 314 is formed by sandwiching theRF 302 between two lites of glass 304,308, as previously discussed. Thecorresponding construction sequence may be described as[G/RP/G/air/prism]. Shaping the air cavity 440 as a wedge, as shown inFIG. 4(H), provides an additional benefit of constructing an embodiment442 of the mirror assembly with the use of only standard, off-the-shelfglass plates (304, 308, and 444). The sequence of components and mediacorresponding to the embodiment of FIG. 4(H) may be listed as[G/RP/G/prism-shaped air/G]. The wedge-shaped cavity 440 may be formed,for example, by disposing the laminate 314 and the plate 444 at anappropriate angle A and sealing the non-uniform peripheral gap along theedge of the plates 304 and 444 with a perimeter seal. It would beappreciated that any air-gap (including the wedge-shaped air-gap), onceformed, may be filled with a clear adhesive material (such as urethane,silicone, epoxy, acrylic, PVB or equivalent materials), liquid (such asmineral oil, glycol, glycerin, plasticizer, propylene carbonate or thelike), or gel, if desired. In constructing such prismatic mirrorstructures, supplemental transparent layer and opaquereflectance-enhancement layers can be applied to any substrate surfaceother than the surface closest to the viewer. Enhancement of reflectancecharacteristics of the embodiments of the invention is discussed below.The air cavity may be formed in other locations as desired, e.g.,between the flattened reflective polarizer and a substrate element. In arelated embodiment, the optically anisotropic film used in a laminatemay be cast, coated or fabricated directly onto the optically flatsubstrate or glass and may not require further processing to achieveoptical characteristics desired for use as a high quality mirror such asan automotive rear-view mirror. Any component used as a substrate or asuperstrate for the APBF must possess optical quality to pass alloptical requirements corresponding to the intended use of the finalproduct. In contradistinction to the use of PVB in a windshieldlaminate, the unique reflecting qualities of the APBF do not compensatefor the optical deficiencies of the substrate or superstrate surfaceadjacent to the APBF in present embodiments. Therefore the substrate andsuperstrate surfaces adjacent to the APBF, in general, must initiallyhave acceptable optical properties for a given application. Inparticular, the quality of the glass surface in contact with APBF thatis closer to the observer is more critical. In comparison, surfaces ofan optical component that are not in contact with the APBF may have adifferent level of optical quality without the inducing unacceptabledistortion characteristics into the finished assembly.

C) Embodiments Employing an EC-Element.

A simplified scheme, not to scale, of an embodiment 600 of the mirrorassembly is shown in FIG. 6 in a cross-sectional view. The APBF film602, which is a part of the laminate 606 shared with the EC-element 608,is a 5 mil thick DBEF-Q film manufactured by 3M Inc. A substrate 610 ofthe laminate 606 includes a 1.6 mm thick soda-lime glass plateperforming as a back plate for an approximately 137 μm thick chamber 614that contains EC-medium. A superstrate 620 of the laminate 606 includesa 1.6 mm soda-lime glass plate 620 that is overcoated, on the surface624 facing the APBF film 602, with a thin-film stack 630 including, inthe order of deposition, approximately 450 Å of titania, TiO₂, andapproximately 150 Å of indium tin oxide, ITO. The chamber 614 containingthe EC-medium is formed by the back glass plate 610 (having surfaces 632and 634) and a front glass plate 635 (having surfaces 636 and 637). Eachof the plates 610 and 635 is coated, on the respective surfaces 632 and637 facing the chamber 614, with a transparent conductive coating suchas ITO (the half-wave optical thickness of which may be chosen at aselected wavelength or as a mean value for a spectrum, for example).Some embodiments of the EC-chamber are discussed in a commonly assignedU.S. Pat. No. 6,166,848, which is incorporated herein by reference inits entirety. Another surface of the plate 610—surface 634—is coated, inthe area outside of the laminate assembly as viewed along the z-axis,with a thin-film stack 638 comprising chromium-ruthenium-chromiumlayers, as described in U.S. Pat. No. 7,379,225. The variousabovementioned thin-film layers can be fabricated by a variety ofdeposition techniques such as, for example, RF and DC sputtering, e-beamevaporation, chemical vapor deposition (CVD), electrodeposition, orother suitable deposition techniques. Embodiments of the invention arenot limited to using a given deposition method for these or other thinfilm coatings.

As discussed above, the display subassembly shown in FIG. 6 as 639 andin FIG. 18 as 1850 may be optionally disposed behind the laminate 606(i.e., adjacent to the surface 640 of the plate 620). In the followingdescription, the display subassembly will be interchangeably labeled aseither 639 or 1850. In such a case, the embodiment 600 may be viewed bythe observer 115 as exhibiting three distinct areas: the transflective,“display” region 642, through which light generated by the displayassembly may propagate through the laminate 606 and the EC-chambertowards the observer, and the outer, reflective region(s) 644 adjacentto the transflective region. As shown in FIG. 6, the APBF 602 coversonly a display portion 642 of the mirror structure 600. In a relatedembodiment, the APBF 602 and/or the resulting laminate 606 may cover thefull FOV of the mirror assembly, i.e. both the display zone 642 and anopaque zone 644. In such an embodiment, all of the surface 634 of theplate 610 may be laminated over with the APBF. Table 2 lists therelative color and brightness characteristics, according to CLELAB, forthe display and opaque regions, 642 and 644, respectively, of thelaminate-containing reflector described in reference to FIGS. 5 and 6.Display (transflective) area of the mirror system: L*=76.7, a*=−2.7,b*=−1.8, reflectance (interchangeably referred to as Y or Cap Y)=51%,Opaque (non-display) area of the mirror system: L*=77.5, a*=−2.3,b*=1.1, reflectance=52.5%.

TABLE 2 (Adjacent) Display Area Opaque Area L* 76.7 77.5 a* −2.7 −2.3 b*−1.8 1.1 Reflectance 51% 52.5%

From the position of the observer 115, the surfaces 636, 637, 632, 634,624, and 640 of the structural elements of the assembly such as glassplates are viewed as the first, the second, the third, the fourth, thefifth, and the sixth surfaces, respectively, and may be alternativelylabeled with roman numerals as I, II, III, IV, V, and VI, as shown inFIG. 6, to indicate their position with respect to the observer. In thisembodiment, surface I corresponds to a front, or proximal, side of theEC-mirror element 608 and surface IV corresponds to a rear, or distal,side of the EC-mirror element 608, with respect to the observer.Generally, the chosen surface numbering applies to any embodiment of thepresent invention. Specifically, surfaces of the structural elements(such as substrates) of an embodiment of the invention are numericallylabeled starting with a surface that corresponds to the front portion ofa rearview assembly and that is proximal to the observer.

The use of the APBF-containing laminate in conjunction with a lightsource in a rearview mirror assembly, for the purposes of increasing theeffective brightness of the light source on the background of theambient light, may be particularly advantageous when the employed lightsource generates polarized light that is preferentially transmitted bythe APBF. Light sources emitting either partially or completelypolarized light—such as displays equipped with an LED, or a laser diode,or an LCD—provide particularly suitable examples. When the displayassembly 639 comprises an LCD, the front polarizer of the LCD may bereplaced with the laminate of the invention. In an alternativeembodiment, a substrate of the LCD, through which light exits the LCD,may be used as a superstrate for a laminate of the invention. In thiscase, a reflective polarizer included within the laminate of theinvention may be used to transmit light having the first polarizationand generated by the display located behind the laminate, and to reflectlight having a second polarization that is orthogonal to the firstpolarization.

Referring again to FIG. 6, a series of laminates 606 were fabricatedusing an embodiment of the process of the invention that included atleast (i) vacuum bagging of the composite comprising the EC-element 608(performing as a substrate), the APBF 602, and the superstrate 620having the coating 630 on its inner surface 624, and (ii) autoclavingthe composite at a temperature within a range from about 80° C. to about110° C. and a gauge pressure of about 100 psi to about 400 psi for atleast 15 minutes. Alternative ranges of processing parameters arediscussed elsewhere in this application. The EC-element was fabricatedaccording to the principles described in U.S. Pat. Nos. 5,818,625 and6,870,656. The suitability of any of the resulting laminate-containingmirror structures for use in the automotive image-preserving reflectorsis demonstrated in FIG. 5, showing a substantially distortion-free imageof the etalon grid formed in reflection 648 of incoming light 650 by theembodiment 600 of FIG. 6. As discussed above, a successful visualevaluation test is defined by an image that is substantially free fromimage distortions. As shown in FIG. 5, the image is continuous acrossthe full FOV of the embodiment 600, the FOV spanning both the displayregion 642 and the outer region(s) 644. In another embodiment, smalldifferences in hue and brightness of the image portions formed by theregions 642 and 644 of the element 600 may be used advantageously toallow easy visual location of the display in the “off” state.

The following examples, described with reference to FIGS. 8(A-J),illustrate advantages of using a reflective polarizer laminated, inaccordance with embodiments of the present invention, within anautomotive rearview mirror assembly that includes a display (an LCD, orotherwise) positioned behind the mirror system. Various datarepresenting optical parameters of the system such as reflectance,transmittance, and absorbance are provided as eye-weighted values (i.e.,for light centered at 550 nm). While the examples of mirror systems andassemblies discussed with reference to FIGS. 8(A, D-G) incorporate anelectrochromic element and an LCD, it is understood that any other typeof automotive mirror element—such as, e.g., a prism mirror element—canbe utilized, and, similarly, that any other suitable type of display maybe used. Discussion of light throughput from a display through aparticular embodiment of the mirror system towards the user assumes theoriginal luminance of the reference display, at the display output, tobe 8,000 cd/m². This value is not limiting but chosen arbitrarily forthe purposes of performance comparison among various embodiments.

FIG. 8(A) shows a prior art embodiment comprising an EC element 800formed by EC-medium secured, within a chamber 614 formed by the firstand second lites of glass (i.e., glass plates) 635 and 610, with aperimeter seal 802 made of a sealant such as epoxy. As shown, anapproximately 145 μm thick ITO coating 817 is applied to the secondsurface (denoted as II, in accordance with the convention defined above)of the first lite of glass 635. The third surface (surface III, of theglass plate 610) is coated with a three-layer coating 804 consisting ofa layer 812 of TiO₂ deposited directly on the second lite 610, an ITOcoating 808 on the TiO₂ layer, and a layer 816 of a metal coatingcomprising an alloy of silver and gold, the concentration of gold beingabout 7 weight-%. Seal 802 may or may not be in physical contact withboth glass plates 610 and 635. As shown, the seal 802 provides a bondbetween the coating 804 and 817. The thicknesses of the coating layers808, 812, and 816 are adjusted to provide for the approximately 55%overall reflectance of the EC element 800. The overall transmittance ofthe EC-element 800, measured for unpolarized light, was in the range ofabout 29% to 33%. These reflectance and transmittance levels areselected to provide a generally suitable compromise between the displaylight output, reflectance intensity and ability to make the displaycomponents behind the mirror system to be unperceivable by the observer115. The brightness of an LCD subassembly 639 (emitting light withluminance of about 8,000 cd/m² towards the EC element 800, as shown withan arrow 820) perceived by the observer 115 corresponds to the reducedluminance of about 2,000 cd/m² due to losses upon the propagation of theLCD-generated light 820 through the element 800.

In contradistinction with prior art and in accordance with the presentinvention, an embodiment of a laminate 828 containing a reflectivepolarizer 824 (e.g., an APBF manufactured by 3M, Inc.) may beadvantageously incorporated within a rearview mirror assembly. As nowdescribed in reference to FIG. 8(B), the reflective polarizer 824 waslaminated, according to an embodiment of the method of the invention, toa surface I of a single 1.6 mm thick lite of glass 826. A resultingtransflective laminate 828 was characterized by the overall (unpolarizedlight) reflectance of about 51.1%, and the overall transmittance ofabout 46.5%, with the loss on absorption being about 2.4%. Since theabsorbance of the glass plate 826 was about 0.7%, the absorbance of thereflective polarizer 824 was estimated to be about a 1.7%.

FIG. 9(A) graphically presents a measured spectral dependence of thereflectance of the laminate 828 of FIG. 8(B). For the purposes ofcomparison, optical performance of the embodiment 828 of FIG. 8(B) wasalso calculated with a thin-film design program, using a thin-film stackof 145 alternating layers having refractive indices of 1.35 and 1.55 tosimulate the APBF 824. The thickness of the layers was optimized via aSimplex algorithm so that the reflectance and transmittance matched thevalues measured with embodiment of FIG. 8(B). The values oftransmittance and reflectance calculated based on the human eye'ssensitivity, are 46.4% and 51.3%, respectively, demonstrating goodagreement with empirical results discussed above. Specific birefringentproperties of the APBF films of the embodiments of FIGS. 8(A) through8(I) were not incorporated in the thin-film design model.

Referring now to the embodiment 830 in FIG. 8(C), the APBF 824 islaminated to two lites of glass, 826 and 832, between surfaces II andIII. The Y reflectance value was within a range of about 48% to about51% and the Y transmittance value is within a range from about 47% toabout 49%. Here, a portion of light 820 penetrating, through the plate826 and the APBF 824, towards the glass plate 832, is reduced due to thehigh value of reflectance of the reflective polarizer 824. In comparisonwith the embodiment 828 of FIG. 8(B), the overall absorption of theembodiment 830 is higher by about 0.4%. The slight reduction ofreflectance figure may be due to either variations in the properties ofthe APBF 824 or, alternatively, due to the change in refractive-indexcontrast at the APBF-surface facing the viewer 115. The modeling of theoptical characteristics of the embodiment 830 resulted in values ofabout 44.1% and about 52.5% for the Y reflectance, the polarizedtransmittance (PT) value of about 89.5%, and transmittance of lighthaving polarization orthogonal to that of the display-generated light ofabout 3.1%. The measured spectrum of overall reflectance of theembodiment 830 in comparison with that of the embodiment 828 of FIG.8(B) is shown in FIG. 9(B) in dashed line.

FIG. 8(D) depicts an embodiment 836 of a rearview mirror assemblycomprising an EC-element 840, which includes the two glass plates 610and 635 that are appropriately overcoated, at surfaces II and m, withITO layers and that form the EC-medium chamber 614, and the embodiment828 of the laminate of FIG. 8(B), bonded to the surface IV of the glassplate 610. During the fabrication process, the EC-chamber 614 is formedby filling the gap between the plates 610 and 635 with an EC-medium andsealing it along the perimeter with an appropriate material such asepoxy. The reflective polarizer 824 is then laminated to the surface IVof the electrochromic element with the addition of a third lite of glass(i.e., plate 826). Alternatively, the reflective polarizer 824 may befirst laminated between the lites 826 and 610, followed by the formationof the EC cavity 614 and the EC-element 840. Alternatively or inaddition, the plate 826 may be made of plastic or other transparentmaterial having suitable optical and physical properties. As described,therefore, the plate 610 may be viewed as a laminate substrate and theplate 826 may be viewed as a laminate superstrate. The overallreflectance and transmittance of this embodiment were measured to bewithin a range of 42% to about 48%, and within a range of about 41% toabout 47%, respectively. In comparison with the above-discussedembodiments 828 and 830, the reflectance values are substantiallyreduced due to the absorption of light in the EC-element 840. Here, theoverall absorbance of the embodiment 836 was about 9% to 11%. In thecase of optimal orientation of the laminate 828 (corresponding to thesituation when the transmission axis of the RP 824 is collinear with thepolarization vector of linearly polarized light 820 generated by the LCD639), the optimal transmittance for polarized light 820 (also referredto herein as the polarized transmittance value, PT) ranges from about75% to about 85%, and that for light having the orthogonal polarizationranges from about 3% to about 5%. When the LCD subassembly 639 producesan output of 8,000 cd/m², the net effective luminance of the displayperceived by the viewer 115 in transmission through the embodiment 836is about 6,720 cd/m². The experimentally measured spectral distributionof the overall (unpolarized light) reflectance of the embodiment 836 isshown in FIG. 9(C) in a solid line, in comparison with that forembodiment 830 of FIG. 8(C), shown in a dashed line. The values ofreflectance and transmittance for the embodiment 836 are about 47.2% andabout 41.5%, respectively. The modeled absorbance is about 11.3%, whichis similar to the experimentally obtained results.

In comparison to the embodiment 836 of FIG. 8(D), the embodiments ofFIGS. 8(E-G) include supplementary coatings, added to increase thereflectance of corresponding mirror assemblies. An embodiment 844 ofFIG. 8(E), for example, includes a bi-layer 846 consisting of a layer ofTiO₂ and an ITO layer deposited, in that order, onto the surface IV ofthe lite of glass 610 prior to laminating the reflective polarizer 824.The bi-layer 846 is designed to be a thin-film structure with apredetermined thickness, e.g., a quarter-wave optical thickness at 550nm. Any measure, taken to modify optical characteristics of the mirrorstructure at the reference wavelength, will affect the visuallyperceived performance of the structure such as the effective luminanceof ambient light reflected by the mirror assembly to the user 115. Theaddition of the bi-layer 846 increases the overall (unpolarized light)reflectance to about 48% to 55% and decreases the transmittance to about33% to 42%, in comparison with the embodiment 836. The transmittance,from the display 639 to the user 115, of light 820 with the preferredpolarization is about 68% to 76% and that of light with orthogonalpolarization is about 3% to 5%. The net throughput of thedisplay-generate light through the embodiment 844 is about 5,930 cd/m²,

Comparing now the embodiment 850 of FIG. 8(F) to the embodiment 844 ofFIG. 8(E), in the former the TiO₂/ITO bi-layer 846 is deposited on thesurface V of the glass plate 826 prior to the lamination of the RP 824between the glass plates 826 and 610. As a result, the overallreflectance of the assembly 850 is about 48% to 55%, which is similar tothe reflectance of the embodiment 844 of FIG. 8(E). The overall(unpolarized light) transmittance, however, is decreased to about 33% to42%. The transmittance value obtained for light of optimal polarizationis about 68% to 76%, while that for light having an orthogonalpolarization is about 3% to 5%. The net luminance, of thedisplay-generated light, perceived by the user 115 through theembodiment 850, is about 5,460 cd/m². It appears, therefore, that incomparison with the embodiment 850, the major effect produced byreversing the order of the bi-layer 846 and the APBF 824 is the slightdifference in the optimal transmittance of light having preferredpolarization. This may be due to either the experimental variability inthe measurement process or variations in the materials used inconstructing the optical system.

In the embodiment 860 of FIG. 8(G), the TiO₂/ITO bi-layer 846 isdisposed on surface VI of the glass plate 826. Such positioning of thelayer 846 results in the overall (unpolarized light) reflectance ofabout 55.1%, while the overall (unpolarized light) transmittance isabout 31.4%. The transmittance of light having the optimal polarization(i.e. polarized transmittance value, PT) is about 59.6% while thetransmittance of light with the orthogonal polarization is 3.1%. The netthroughput of the display light 820 through the embodiment 860 is about4,770 cd/m². Comparison of the experimentally determined spectra forreflectance of the unpolarized light for embodiments of FIGS. 8(D-G) ispresented in FIG. 9(D).

In another embodiment of the invention, schematically shown in FIG. 8(H)in an exploded view, the APBF 824 is laminated between the plate 826 andthe EC-element 877, which are all disposed in front of the LCD 639 and alight engine 870. As shown, a conventional LCD 639 includes an LC-medium872 sandwiched between two polarizers, an entrance polarizer 874 and anexit polarizer 876, and is smaller than the EC-element 877. As a result,the display area (transflective area) of this embodiment has a lesserlateral extent that that of the whole mirror system. It would beappreciated, however, that a concept of a “full-mirror” display, where adisplay or a plurality of displays located behind the mirror systemoverlaps, in projection onto the viewable surface of the mirror system,with most or all of this viewable surface, is also contemplated by thevarious embodiments of this invention. A particular shape of either themirror system or a (group of) display(s) does not affect the underlyingprinciple of the embodiment of the invention. Schematic examples of suchdisplay(s) forming a “full-mirror” group of displays, positioned behinda mirror system 5200, is shown in assembly embodiments 5210 and 5214 ofFIGS. 29(A, B). In particular, FIG. 29(A) illustrates a single display5216 that is substantially co-extensive with the viewable surface of themirror system 5200, while FIG. 29(B) shows three discrete displays 5220,5222, and 5224 forming a “full mirror” display within the assembly 5230.

If further reference to FIG. 8(H), optimization of light transmissionfrom the light engine or light source 870 through the LCD 639 throughthe laminate 828 towards the EC-mirror system 877 may be achieved byorienting the APBF 824 so as to have its transmission axis 878 to becollinear with the transmission axis 880 of the exit polarizer 876 ofthe LCD. The transmission axis of the entrance polarizer 874 of the LCDis denoted as 882. (Optionally, the orientation of the polarizer 874 inthe xy-plane may be changed if desired so as to rotate the axis 882 by apredetermined angle, e.g., ninety degrees, to change the display modefrom “bright” to “dark.”) In this “maximum transmission” orientation,the RP 824 transmits approximately 88.5% of polarized light 820emanating from the LCD 639 generally in +z direction and reflects about50% of the unpolarized ambient light (not shown) incident upon thelaminate through the EC-element 877 back to the viewer 115 (not shown).In this case, the brightness of the LCD subassembly 639 having luminanceof 8,000 cd/m² would be perceived by the viewer 115 as corresponding toabout 7,080 cd/m². In a minimum transmission orientation of the RP 824(corresponding to a setting in which the transmission axes 878 and 880are substantially perpendicular, not shown) the transmission of lightfrom the LCD 639 to the viewer 115 drops to about 3.8%. Incontradistinction, the polarization-insensitive transflective elementsof prior art, such as those comprising the embodiment of FIG. 8(A),would not be capable of simultaneously attaining the 88% transmittanceand 50% reflectance. It is worth noting that, generally, a frontpolarizer 876 of the LCD 639 can be removed, in which case the properlyoriented RP 824 can operate as the front polarizer of the LCD. In anembodiment of a display employing the absorptive polarizer the RP may beused instead of the absorptive polarizer. In this case, the extinctionratio, i.e., the ratio of intensities of light with two orthogonalpolarizations, will affect the effective contrast ratio of the display.Preferably, the transmittance of light with the off-axis polarizationstate (the polarization state when the LCD is in the off position)should be less than 5%, preferably less than 2.5%, more preferably lessthan 1% and most preferably less than 0.5%. The lower transmittancevalues of the off-axis polarization state leads to images with darker“black” parts of the image.

D) Specific Embodiments of a Switchable Mirror System Employing aLiquid-Crystal Cell and an EC-Element.

Switchable mirror system (SMS) embodiments may employ variousLC-cell-based devices such as, e.g., one or more cells containing acholesteric LC-material, which manipulates (transmits and/or reflects)circularly polarized light and used with or without an additionalquarter-wave plate. Embodiments may also employ a Twisted Nematic (TN)cell, a Super Twisted Nematic (STN) cell, a guest-host or phase-changeLC device incorporating a dichroic dye, a Ferroelectric LC device suchas a smectic ferro-electric cell, a nematic Distortion of Aligned Phases(DAP) LC device, an In-Plane Switching (IPS) device; an OpticallyCompensated Bend (OCB) device, or a Multi-Domain Vertical Alignment(MVA) device, which manipulate (transmit and/or reflect) linearlypolarized light. Although the following embodiments of a switchablemirror system are described in reference to a TN LC-cell, it isappreciated that any of the above-mentioned devices can be generallyused to provide for switchable operation of a mirror system. To reflectlight of red/green/blue (RGB) colors in a particular circularpolarization (right-handed, for example), three cholesteric LC-cellswould be required. Therefore, it would require six cholesteric LC-cellsto reflect RGB colors in both circular polarization. Broadbandpolychromatic Circularly polarized light can be reflected by acholesteric cell containing a variable pitch medium, but because of thedifficulty in forming the variable pitch difficulty, this technology hasnot been successfully commercialized. Cholesteric LC-based systems are,in addition, very temperature-sensitive because the cholesteric pitchlength changes with temperature. This change results in atemperature-dependent shift in the wavelength of reflected light over aslittle as a 10 deg C. temperature range. Automotive mirrors, as well asarchitectural and aerospace windows must perform over a largetemperature range (−40 deg C. to 80 deg C.), thereby making the use ofcholesteric systems impractical for these applications. Therefore,devices that manipulate linearly polarized light (such as a TN LC-cell)are preferred.

For simplicity of illustrations, FIGS. 33(A,B) show no coatings such astransparent electrically conductive coatings or reflective or absorptiveor other functional coatings such as alignment or passivation coatingsof the embodiment that may be present on various surfaces of illustratedembodiments as described in reference to other drawings in the presentapplication. Similarly, no auxiliary elements such as electricalconnections between or among various layers, or mechanical componentssuch as holders, clips, supporting plates, or elements of housingstructure are depicted, although practical implementations of thediscussed embodiments may contain all these features. Embodiment 3300 ofFIG. 33(A) employs a switchable mirror system 3302 configured on thebasis of an auxiliary TN LC-cell 3303 that includes substrates 3304 and3306 and a seal 3308 encasing an LC-layer 3310. The embodiment furthercontains two APBF-based reflective polarizers 3311 and 3312 that arelaminated between the LC-cell 3303 and a lite of glass 3314 and the LCcell 3303 and a lite of glass 3315, respectively, according to anembodiment of the method of the invention as described herein. As knownin the art, the twisted nematic effect is based on the preciselycontrolled realignment of LC molecules between differently orderedmolecular configuration under the action of an applied electric field.The LC-cell 3303 was configured so as to rotate by 90 degrees thepolarization of light incident upon the cell when no voltage is appliedto the cell (i.e., in the “off” state). In an actual structurefabricated according to the embodiment of FIG. 33(A), the linearlypolarizing APBF-layers 3311 and 3312 were oriented so as to have theirpolarization axes mutually parallel. Accordingly, the resulting“off”-state reflectance and transmittance of the mirror system 3302 weremeasured to be 88% and 6%, respectively, for unpolarized light incidentupon the system generally along the z-axis. The “off”-statecharacteristics of an embodiment 3302 of a switchable mirror system ofthe invention measured in unpolarized light may be generally referred toas “high reflectance/low transmittance” (or “high R/low T”) state. Whenthe LC-cell was energized (“on”, with voltage applied), however, theLC-cell 3302 did not rotate polarization of light incident upon thecell, and characteristics of the mirror system 3302 measured inunpolarized light included 50% reflectance and 41% transmittance. The“on”-state characteristics measured in unpolarized light may be referredto as “mid R/high T” state. The same system 3302 was also characterizedin polarized light 820 emanating from the display 1850. Provided thatthe operation of the embodiment was optimized, namely, that polarizationof light 820 emanating from the LCD 1850 towards the viewer 115 wasaligned with the polarization axes of the APBFs 3311 and 3312, suchpolarized light throughput of the mirror system 3302 from the LCD 150towards the viewer 115 in the “on” state of the LC-cell was measured tobe 76%. It is understood that, in practice, an additional EC-element ora prism element may be optionally employed in front of this embodiment,as viewed by the viewer 115.

FIG. 33(B) illustrates an embodiment 3330 that is structurally similarto the embodiment of FIG. 33(A). In fabrication of this embodiment,however, a polarizing layer 3334 placed in the laminate between theLC-cell 3303 and an optional first substrate 3314 was a typicalabsorbing polarizer. Polarization axes of the APBF 3311 and theabsorbing polarizing layer 3334 were mutually parallel. In thisembodiment, the “off” state reflectance and transmittance of theswitchable mirror system 3340 measured in unpolarized light were,respectively, 41% and 3%. This state of operation of the system 3340 maybe referred to as “mid R/low T”. In comparison, in the powered (“on”)state the reflectance and transmittance of unpolarized light was 6% and38%, respectively (“low R/high T”). It will be understood that,generally, in any “low reflectance” state a dominating contribution tothe total reflectance of the device and the optical quality of an imageformed in reflection by the mirror system is provided by light reflectedoff of the first surface of the device (such as surface I in FIG.33(B)), and not the surfaces of the absorbing polarizer (surfaces II andIII). If the surface of the substrate is optically flat such as withmost glass substrates, the optical quality of the mirror device in itslow reflectance state is suitable for use as an automotive mirror. Thereflectance of the mirror in the low reflectance state is comparablewith the first surface reflectance of a prism in its low reflectancestate. The same system 3340 was characterized in polarized light 820emanating from the display 1850. The optimized throughput of light fromthe LCD 1850 (i.e., when polarization of light 820 was aligned withpolarization axes of polarizers 3311, 3334) to the viewer 115 with theLC-cell 3303 powered “on” was measured to be 69%. This embodiment isparticularly advantageous for use with a display, for example a TFT-LCDvideo screen. Because the reflective polarizer is behind the LC element,with respect to the viewer 115, the embodiment 3330 has very lowreflectance in the “on” state that is essentially equal to thereflectance of the first surface. As a result, the embodiment 3330produces very low glare in incident ambient light. Consequently, whenthe display 1850 is “on” a combination of the low glare and the hightransmittance of the embodiment due to the alignment of polarization ofthe light 820 with the transmission axis of the APBF 3311 results in ahighly contrast image.

As mentioned in reference to FIG. 4(D), embodiments of any LC-cell-basedswitchable mirror system of the invention may additionally incorporate aprismatic element. Alternatively or in addition, an embodiment of aswitchable mirror system may employ a combination of an LC-based-deviceand an auto-dimming mirror structure such as one containing anEC-element.

Example 1

An example of such embodiment is illustrated in FIG. 34. As shown, theembodiment 3400 includes a TN LC-cell and an EC-cell. A switchablemirror system 3410 was fabricated as a combination of the EC-mirrorelement 840 (140 micron wide EC-chamber filled with EC-fluid)) and theTN LC-cell 3303 (LXD Inc., Cleveland, Ohio). The sample of the mirrorsystem further included one APBF 3312 (DBEF-Q) laminated between theelement 840 and the substrate 3304 of the LC-cell 3303 and another APBF3311 (DBEF-Q) laminated between the LC-cell 3303 and the lite of glass3315. The thickness of glass lites was approximately 1.6 mm. (Variousoptical coatings, electric connections, and housing elements necessaryfor proper operation of either the LC-cell or the EC-mirror element anddiscussed elsewhere in this application are not shown in FIG. 34 forsimplicity of illustration.) The polarization axes of both polarizers3311 and 3312 were aligned. When both the LC-cell 3303 and theEC-element 840 were in the “off” state (no voltage applied to either ofthem), the reflectance and transmittance of the system 3410 weremeasured in ambient, unpolarized light to be 72% and 6%, respectively.Such operational state of the embodiment 3410 may be referred to as“high R/low T” state. With the LC-cell being powered “on” and theEC-element 840 being still “off”, the system 3410 demonstrated, inambient unpolarized light, the reflectance of 42% and the transmittanceof 37%, This state of operation is characterized by intermediate levelof reflectance and high level of transmittance and may be referred to as“mid R/high T” state. It is understood that when both the LC-cell andthe EC-cell are powered “on”, both the reflectance and transmittance ofthe embodiment 3410 measured in unpolarized light will be low (“lowR/low T”). In comparison, performance of the system 3410 was alsomeasured in polarized light (such as light output 820 from the LCD 1850having optimal polarization aligned along the axes of the polarizers3311, 3312). When the LC-cell 3303 is “on”, the system 3410 throughputof such optimally polarized light from the LCD 1850 to the viewer 115was measured as 75%.

Example 2

Another sample of the switchable mirror system was also fabricatedaccording to the structure 3410, with polarization axes of the RPs 3311and 3312 mutually aligned. The EC-element 840 included two glasssubstrates, each approximately 6 cm by 26 cm in size and 1.1 mm thickand carrying approximately 145 nm thick ITO electrode layers on thesurfaces forming the EC-chamber. The EC-chamber of approximately 140microns in width was assembled with the use of amine cure epoxy andfilled with EC-fluid comprising 27 mM of the anodic material 5,10dimethyl 5,10 dihydrophenazine and 32 mM of the cathodic materialoctylviologen tetrafluoroborate. The RPs 3311, 3312 were made of DBEF-Qsold by 3M Corp. of St. Paul, Minn. and flattened and laminatedaccording to the method of FIG. 3. The TN LC cell 3303 comprising twopieces of 1.1 mm glass was purchased from LXD Inc. of Cleveland, Ohio.The TN LC-cell based device was segmented, as described elsewhere inthis application, to allow for independent activation of multiple areasof the mirror system. There were a total of 23 segments of various sizesand shapes contained within this switchable mirror, as schematicallyshown in FIG. 56(A).

The switchable mirror system of Example 2 was assembled according to themethod described in reference to FIG. 3. In Example 2, the EC-element840, the TN LC-cell element 3303, and the back glass 3315 wereappropriately configured to have transverse offsets to allow electricalbuss clips to be applied to both electrodes of the EC-element as well asto both electrodes of the TN LC-cell device. Offsets in the TN LC-cell3303 allowed the ground plate to be contacted on the side while thesegments of the other electrode could be contacted on both the top andbottom of the substrate. Buss clips were added to the EC-element offsetand to the TN LC-cell offsets so as to allow activation of each elementindividually. Table 2A summarizes discrete states ofreflectance/transmittance of unpolarized light by the switchable mirrorsystem of Example 2. (The “high T” value of 41.9% measured inunpolarized light corresponds to approximately 80% transmittance ofoptimally polarized light output from the LCD 1850.)

TABLE 2A Status of EC-cell Status of TN Level of Level of 840 LC-cell3303 reflectance, % transmittance, % Power ON Power OFF 6.0 (“low R”)0.8 (“low T”) Power OFF Power OFF 79.7 (“high R”)  7.0 (“low T”) PowerON Power ON 5.5 (“low R”) 4.8 (“low T”) Power OFF Power ON 47.6 (“midR”)  41.9 (“high T”) 

Generally, the embodiment 3400 has advantageous characteristics thatcome from its ability to combines a rapid response of an LC-cell-basedswitch with a large dynamic range of an EC-element. Specifically, due tothe fast performance of the LC-cell 3303 the embodiment 3400 can beswitched from a high-reflectance (in excess of 70%) state to alow-reflectance (several %) state very rapidly, (within approximately100 milliseconds). At the same time, the EC-element can gradually(within 1 to 5 seconds) reduce the reflectance of the overall systemfrom “high R” state or an intermediate-reflectance state (“mid R”, wherethe value of R is approximately between 35% and 70%) to a “low R” state(R of about a few percent) or, if required, to any other specified levelof reflectance. As demonstrated below, the reflectance of an embodimentof the overall APBF-containing mirror system can be varied bycontrolling the absorption of light in the components of the system suchas an EC-element or, generally, an electrooptic element located in frontof reflecting layers.

It is appreciated that alternative implementation of a switchable mirrorsystem may include wire-grid reflective polarizers used instead ofAPBF-based reflective polarizers in either of the embodiments of FIG.33(A, B) or 34. In comparison with the APBF-based RPs, wire-gridpolarizers require no flattening and can be used as electrodes and evenas alignment layers for the LC-medium.

Segmentation of a Mirror System:

Overall, embodiments employing a combination of an LC-cell with aprismatic element or an EC-element, such as those of FIG. 4(D), 33, and34, benefit from the ability to rapidly switch the LC-cell-containingmirror system to a “low reflectance/high transmittance” state so as tomaximize transmission of the image produced by the LCD 1850 to theviewer 115, and so as to maximize contrast ratio of the image (byminimizing the reflectance of ambient light, as is taught in the U.S.2009/0207513). In a specific embodiment, the LC-cell-based switchablemirror system of the invention can be further segmented by formingmultiple pixels or shutters in the LC-element as known in the art, e.g.,as illustrated in FIG. 45. The shutter segmentation would allow forindependent and, if required, programmable and reconfigurable modulationof different portions of the mirror system. Consequently, a segmentedembodiment would allow the user to modify optical characteristics of achosen mirror segment, e.g., a segment of the mirror situated directlyin front of a particular component located behind the mirror (such asdisplay of the switchable mirror assembly).

Components located behind the segmented portion of the mirror mayinclude a photosensor, a camera, an icon (indicia) with or without abacklight. If the photosensor that detects glare conditions at night islocated behind the switchable mirror in an eyehole area, thecorresponding “eyehole” area could be segmented in order to remain inthe “high R” stealth mode during daytime (directed by theforward-looking photosensor) and switch to the “mid R/high T” modeduring nighttime. Similarly, when information from a camera locatedbehind the mirror assembly is not required, the segmented area in frontof the camera could remain in the “high R” stealth mode and then switchto the “mid R/high T” mode of operation when image information from thecamera becomes necessary. Such switching could happen at a rateconsistent with the response frequency of the LC-cell based device.Accordingly, operation of the camera, the sensor, the lighted icon orthe indicator could be modulated at the rate of switching of acorresponding segmented area of the switchable mirror so that picturesor measurements are taken, or the icon or indicator light source isturned on and off, only during the periods of “high transmittance” ofsuch segmented area of the SMS. (At a switching rate of about 30 Hz orhigher, for example, the human eye would not detect the “flicker” of theswitching event.) Depending on the requirements of the system, therelative on/off time, period, and duty cycle of switching of aparticular segment of the SMS can be adjusted to balance the needs ofthe sensor (or the camera) and the desire to maintain a stealthappearance for the mirror. If the camera or sensor is sensitive toaberrations caused by polarized light, a de-polarizer could be placed infront of the camera or sensor. Likewise, a visual icon or indicia can behidden behind a segmented portion of the mirror in the “high R” mode andmade visible (preferably with a backlight switching on) at the same timeas the corresponding mirror segment switches from “high R” to “midR/high T” mode. All of these examples refer to switching of the TNLC-cell section of the SMS that is positioned between two polarizers.

It should be noted that, generally, any element of the switchable mirrorsystem can be segmented. A EC-element portion of the mirror if presentcan be segmented and selectively switched. So can a GH LC-cell portiondescribed below. Similarly, the TN LC-cell portion of the mirror can besegmented and selectively switched.

In a specific embodiment, the LC-cell could be segmented so as tofacilitate transmission of numeric or alpha-numeric images from thedisplay through a mirror system to the viewer. Alternatively, theLC-cell could be segmented in a dot-matrix fashion. Images could then bedisplayed to the viewer by alternating the high and low reflectionstates of the segments of the mirror system or, if the area is back-lit,by alternating the high and low transmission states of the segments.

Combinations of Liquid-Crystal Cells with Polarizers:

Embodiments of various LC-cells in combinations with polarizers (eitherreflective or absorptive), and an EC-element or a prism element areschematically illustrated in FIGS. 46(A-H). For each of the depictedcombinations, FIGS. 46(A-H) illustrate its operation depending onwhether the LC-cell is powered or not. FIG. 46(A) shows an LC-cell 4602positioned between the absorptive and reflective polarizers 4604, 4606,the polarization axes of which are mutually parallel. The operation ofsuch a combination in different reflectance states depending on whetherthe LC-cell 4602 is powered. FIG. 46(B) shows an arrangement similar tothat of FIG. 46(A) with the polarization axes of the two polarizers4604, 4606 being mutually orthogonal. FIG. 46(C) shows an embodimentcontaining an LC-cell 4602 located between two reflective polarizers4606 with mutually parallel axes. The operation of such a combination indifferent reflectance states depending on whether the LC-cell 4602 ispowered. FIG. 46(D) shows a combination of an LC-cell 4608 containing anabsorbing anisotropic dye 4610 with a reflective polarizer 4606, wherethe absorptive dye absorbs light having linear polarization parallel tothe polarization axis of the reflective polarizer. FIG. 46(E)illustrates a similar embodiment where the anisotropic dye 4610 absorbslight having linear polarization that is perpendicular to thepolarization axis of the reflective polarizer. FIG. 46(F) shows acombination of the cholesteric LC-cell 4611 and a reflective polarizer4606 where the cholesteric molecules 4611 a have random orientation.FIG. 46(G) shows a combination of a reflective polarizer 4606, a LC-cell4602, a quarter-wave plate 4612, and a cholesteric reflective polarizer4614, where the cholesteric material of the polarizer is characterizedby a variable pitch. FIG. 46(H) illustrates two embodiments I, II thatmay be employed in automotive rearview mirror assemblies. The firstembodiment I includes, in order from the viewer, an EC-element 4620, apolarizer 4622 (either absorptive or reflective such as APBF, forexample), an LC-cell 4624, another polarizer 4626 (either absorptive orreflective such as APBF, for example), and an additional supportsubstrate 4628 which can be a front surface of the LCD 4630. In thesecond embodiment II, in comparison with the embodiment I, theEC-element 4620 is substituted with a prismatic element 4632. Each ofthese embodiments I, II represents a corresponding combination of eitheran EC-element or a prism element with a switchable multiple-stageLC-cell-based reflector. In a specific embodiment, a prism element 4632may be substituted with a flat piece of glass. As discussed in referenceto FIG. 33(B), a preferred configuration of LC-cell is such as to permitthe mirror system to have high reflectance when the LC-cell is off. Thediscussion below follows this convention. One of the multiple stages ofoperation of either embodiment I or II of FIG. 46(H), when the LC-cell4624 is “off”, is generally characterized by: a) the overallreflectance, R, of more than 35%, preferably more than 40%, morepreferably more than 50%, even more preferably more that 60%, and mostpreferably greater than 70%; and b) the polarized transmittance, PT, ofless than 10%.

Another stage of operation, when the LC-cell 4624 is on, ischaracterized by: a) the overall reflectance, R, of less than 50%,preferably less than 30%, more preferably less than 20%, and mostpreferably less than 10%; and b) the polarized transmittance, PT, ofmore than 50%, preferably more than 60%, and most preferably more than70%. It is understood that switching among the multiple stages ofoperation of the embodiments I, II of FIG. 46(H) is enhanced by eitherswitching the EC-element or tilting the prism element, depending on theembodiment. In a practical rearview mirror assembly, a light sourceincluding a display may be positioned behind either of theseembodiments. It is understood that implementing various above-mentionedoptical characteristics of any of the embodiments of FIG. 46(H) willalso depend on whether the polarization of light emanating from thedisplay is aligned with the polarization of light transmitted by thecorresponding embodiment in its high transmission stage of operation.

D1) Specific Embodiments of a Switchable Mirror System Employing aCombination of Liquid-Crystal-Cell Based Devices

A rearview assembly incorporating a mirror system and a source of lightsuch as a display behind the mirror system should allow for operation ina “display” mode, when the image formed with the use of light-outputfrom the display is projected through the mirror system for viewing bythe user, as well as in a “mirror” mode, when it is the image of thesurrounding formed in reflection of the ambient light by the mirrorsystem that the viewer pays attention to. It is appreciated that, forthe purposes of the invention, the optimized embodiment of the mirrorsystem in such an assembly should have maximized transmittance andminimized reflectance in the “display” mode in order to assure that thebrightness of the displayed image is optimal, especially when ambientlight is plentiful. In the “mirror” mode, however, the same embodimentof the mirror system should be configured to have transmittance as lowas possible and reflectance as high as possible to assure that amount oflight reaching the viewer from behind the mirror system is minimized sothat the quality of the image of the surrounding does not suffer. Inother words, the dynamic range of reflectance/transmittancecharacteristics in an embodiment of a switchable mirror system (SMS) ofthe rearview assembly should be maximized. From the discussion providedin reference to FIGS. 33 and 34 it is appreciated that embodiments of aswitchable mirror system that are based on either an LC-cell or acombination of an EC-cell and an LC-cell are advantageous in that theypossess significant dynamic ranges of operation. However, it is alsoappreciated that these dynamic ranges of reflectance/transmittancecharacteristics are limited. Specifically, the dynamic range of theexemplary embodiment 3410 was limited by the ability of the embodimentto switch between the “high R/low T” and “mid R/high T” states. Suchlimitation stems from the fact that a typical EC-element operates byabsorbing, in its “on” or “colored” state, light of any polarization andtherefore attenuates both light reflected and light transmitted by themirror system. Such limitation is understood to remain in any mirrorsystem that includes an optical element that simultaneously affectslight in both orthogonal states of polarization.

We have discovered that configuring a mirror system (and, in particular,the switchable mirror system that includes an LC-cell-based device) insuch a fashion as to provide for independent attenuation of lightcomponents having different polarization states further increases theattainable dynamic range of reflectance/transmittance characteristics ofthe rearview assembly for the purposes of the invention. In particular,a switchable polarizer that operates in two modes (transparent for lightwith any polarization in the first mode and absorbing light with aparticular polarization in a second mode) may be incorporated into amirror system. Examples of such switchable polarizer are provided by aGuest-Host Liquid Crystal (GH LC) element containing a dye and anEC-element containing an orientated EC-medium such as stretchedpolyaniline, as described by P. Anderson in Appl. Phys. Lett., 83(7),1307-1309 (2003). This publication is incorporated herein by referencein its entirety. The first example (GH LC-cell with a dye such as ananthraquinone dye or an azo dye) is predominantly used below indescribing embodiments of a switchable mirror system of the invention.It shall be appreciated, however, that the EC-element containing anorientated EC-medium can be used instead of the GH LC-cell, which use iswithin the scope of the present invention.

Incorporating such switchable polarizer as part of a switchable mirrorin front of the SMS that contains an RP allows for selectively absorbinga portion of ambient incident light that is reflected by the RP towardsthe front of the mirror system without significantly attenuating aportion of light having a different polarization.

An exemplary embodiment 5200 configured according to this principle isschematically illustrated in FIG. 52 showing, in side view, a switchablepolarizer 5210 disposed in front of the switchable mirror 5214. Theswitchable mirror 5214 may include, e.g., the SMS 3302 of FIG. 33(A), orthe SMS 3340 of FIG. 33(B), or the SMS 3410 of FIG. 34, or the SMS ofFIG. 34 where instead of the EC-element a prismatic element is used.Although the devices 1850, 5214, and 5210 are shown to be separated fromone another, it is understood that in another implementation some of thesurfaces of at least some of these devices may be in physical contact.For example, the outer surface 5216 of the mirror system 5214 and aneighboring surface 5218 of the switchable polarizer 5210 may beattached to one another. Alternatively or in addition, it is understoodthat the component devices forming an embodiment 5400 may share asubstrate when the embodiment 5400 is configured with the use of themethod of invention described in reference to FIG. 3.

Principle of Operation:

FIGS. 53(A, B) and 54(A, B) illustrate a principle of operation of aspecific embodiment 5300 of a switchable mirror system that includes aTN LC-cell 3303 that is sandwiched between the two APBFs 3311 and 3312and further laminated to a GH LC-cell 5310. The GH LC-cell 5310,corresponding to the front of the embodiment, includes an LC medium 5312serving as a host medium to the molecules of dye 5314 and disposed in acavity formed between two glass substrates 5316, 5318. Each ofcavity-defining surfaces 5320, 5322 of the substrates 5316, 5318 carryan electrically-conductive layer 5324 of TCO (such as ITO, for example)overcoated with an alignment layer 5326 (such as polyimide, PVA, orangularly deposited SiO_(x)) to facilitate the alignment of theLC-molecules along a preferred direction. In the embodiment 5300, the LCfluid 5312 has a positive dielectric anisotropy in that the molecules ofthe host LC medium 5312 and the molecules of the guest dye 5314 arealigned substantially parallel to the surfaces 5320, 5322 when novoltage is applied between the electrode layers 5324 (V₅₃₁₀=0), as shownin FIG. 53(A). However, when the voltage between the electrodes 5324 isnon-zero (V₅₃₁₀≠0), the molecules of the host LC-medium 5312 and themolecules of the guest dye 5314 are rotated and align substantiallyalong the vector of electric field created across the LC-medium 5312, asshown in FIG. 53(B). As a result, when no voltage is applied to the cell5310 (the cell 5310 is “off”) the guest dye absorbs light having alinear polarization component parallel to surfaces 5320, 5322. When thecell 5310 is energized (voltage is “on”) however, the attenuation oflight in any polarization state within the medium 5312 due to absorptionin the dye 5314 is substantially non-existent.

The LC-medium-alignment layers 5326 and the reflective polarizers 3311,3312 are configured within the embodiment 5300 in such a way as toassure that the LC-molecules 5312 (and, accordingly, the dye molecules5314) are aligned predominantly parallel to both reflection axes of theRPs 3311, 3312 (y-axis in FIG. 53(A)) when no electric field is appliedacross the medium 5312.

FIG. 54(A) illustrates a sub-set of FIG. 53(A) and shows that, as aresult of such alignment when no electric field is applied across themedium 5312, a component 5410 of ambient light 5412 incident uponsurface I and polarized along the absorption axis (y-axis in FIG. 54(A))of the dye 5314 will be absorbed by the dye. At the same time, a lightcomponent 5414 having orthogonal polarization (along the x-axis) istransmitted through the GH LC-cell 5310 and the RP 3312 towards the TNLC-cell 3303, as shown by an arrow 5420. If the TN LC-cell 3303 is “on”(V₃₃₀₃≠0), the light component traverses the cell 3303 (in the −zdirection in FIG. 54(A)) and the RP 3311, as shown by an arrow 5422,assuring sufficiently high level of transmission for unpolarized light.(The rearview assembly may be further configured to have this lightcomponent absorbed if necessary, e.g., in the back portion of the mirrorsystem in, e.g., an opacifying layer such as an appliqué layer or apartially transmissive layer disposed in the back of the mirror systemspecifically for this purpose.) If, in addition, surface I of theembodiment 5300 is AR-coated, the reflection of ambient light by theembodiment 5300 will be extremely insubstantial and approaching zero. Itshall be appreciated, therefore, that this operation of the switchablemirror system is characterized by low reflectance and high transmittance(“low R/high T”) of unpolarized light that could not have been achievedin any of embodiments described so far. On the other hand, if the TNLC-cell 3303 is “off” (V₃₃₀₃=0), the polarization vector of thecomponent 5420 is rotated by 90 degrees upon traversal of the cell 3303to a position parallel to the reflection axes of the RP 3311.Consequently, the RP 3311 reflects the light component 5420 towards theviewer 115. The reflected light component 5420 further traverses thecell 3303 and continues to propagate through the mirror system uponreturn to the viewer 115, as shown by arrows 5424 and 5426.

Similarly, in further reference to FIG. 53(B), when voltage required toswitch the GH LC cell 5310 “on” is applied (V₅₃₁₀≠0) between theelectrode layers 5324, the effective absorption in the dye medium 5314of ambient light 5412 is zero, and a portion 5410 of the incident lightthat has polarization vector parallel to the reflection axis of the RP3312 is reflected by the RP 3312 back to the viewer 115. This isschematically illustrated in FIG. 54(B) showing a sub-set of FIG. 53(B).The propagation of a portion 5414 of incident light having an orthogonalpolarization depends on the state of the TN LC-cell 3303, as discussedin reference to FIGS. 53(A) and 54(A): the light component 5414 will bereflected by the mirror system towards the viewer 115 when the cell 3303is “on”.

Table 2B summarizes the discrete states of reflection/transmission ofunpolarized light by the switchable mirror system of the embodiment 5300depending on the operational status of each of the switchable absorptivepolarizer 5310 and the TN LC-cell 3303, as well asreflectance/transmittance values estimated for conventional guest-hostLC media and materials used in fabrication of the TN LC-cell. The “lowR” values represent an embodiment where surface I is not AR-coated.AR-coating of surface I will reduce the values of reflectance evenfurther. In comparison, Table 2B1 summarizes the discrete states ofreflectance/transmittance of unpolarized light by a similar SMS where,instead of the GH LC-cell 5310, an EC-element containing orientatedEC-medium is used.

TABLE 2B Status of Status of cell 5310 cell 3303 Level of ReflectanceLevel of Transmittance Power ON Power High (“high R”); Low (“low T”);OFF Approx 65% to 75% Approx 0.3% to 7% Power Power Intermediate (“midR”); Low (“low T”); OFF OFF Approx 35% to 45% A; pprox 0.15% to 4% PowerON Power ON Intermediate (“mid R”); High (“high T”); Approx 35% to 45%Approx 35% to 45% Power Power ON Low (“low R”); High (“high T”); OFFApprox 6% to 15% Approx 35% to 45%

TABLE 2B1 Status of orientated Status of Level of Level of EC-cell cell3303 Reflectance Transmittance Power ON Power OFF “Mid R” “Low T” PowerOFF Power OFF “High R” “Low T” Power ON Power ON “Low R” “High T” PowerOFF Power ON “Mid R” “High T”

As shown, therefore, an embodiment of the switchable mirror system ofthe invention can be operated in a tri-state reflectance mode (“high R”,“mid R”, and “low R”) to reduce glare or optimize the brightness of thedisplay (specifically, in “mid R” and “low R” modes of operation). Inaddition to that, the embodiment assures an operation in a dualtransmission mode (“low T” to be used when the display 1850 is “off” and“high T” mode to be used when the display 1850 is “on”). A comparisonwith Table 2A shows that the embodiment 5300 offers an advantage overthe embodiment 3400 in that only the former can be operated in a “lowR/high T” mode and thus has a higher dynamic range ofreflectance/transmittance modes of operation.

Gradual Variation of Optical Performance:

It shall be further appreciated, however, that the operation ofembodiments of the invention is not limited to discretereflectance/transmittance levels listed in Table 2C but may be furthercontrolled in a continuous, variable, “grey scale” fashion between theselevels. Specifically, the “grey scale” operation can be achieved byadjusting the voltage V₅₃₁₀ applied to the switchable polarizer 5310 ina continuous fashion. For example, as the applied voltage is graduallyincreased from the zero level, the host-medium LC molecules 5312 and theguest-medium dye molecules 5314 rotate from a default orientationparallel to the chamber wall surfaces 5320, 5322 to that perpendicularto the chamber wall surfaces. Due to this rotation the amount of ambientlight 5412 absorbed by the dye 5314 (FIG. 54(A)) will be graduallyreducing and the amount of light returned to the viewer by the RPs 3311,3312 will be gradually increasing. More specifically, the level ofambient light reflected by the embodiment towards the user can begradually increased from (FIG. 54(B)) “low R” level (corresponding to nolight reflected when V₅₃₁₀=0. V₃₃₀₃≠0, in FIG. 54(A)) through “mid R”level (corresponding to either light 5420 reflected when V₅₃₁₀=V₃₃₀₃=0,in FIG. 54(A) or light 5410 reflected when V₅₃₁₀≠0, V₃₃₀₃≠0, in FIG.54(B)) to “high R” level (corresponding to light 5410 and 5420 reflectedwhen V₅₃₁₀≠0, V₃₃₀₃=0, in FIG. 54(B)) by gradually varying the voltageapplied to the switchable polarizer 5310.

If a rearview assembly incorporating the embodiment 5300 is to operatein a glare-reduction mode with the TN LC-cell 3303 performing in a hightransmission mode (V₃₃₀₃≠0), care must be taken to minimize the amountof light reflected off of assembly components located behind the mirrorsystem. All surfaces behind the mirror system should be coated with anAR coating or be blackened to maintain stealthy appearance. To improvethe stealthy appearance further, a second switchable polarizer 5510 canbe employed. For example, as shown in FIG. 55, an embodiment 5500 of theswitchable mirror can comprise a sequence, starting from the front ofthe rearview assembly, of the first GH LC-cell 5210 and the switchablemirror 5214 (such as, e.g., the embodiment 3303 of FIG. 33(A)) followedby the second GH LC-cell 5510. Here, the second GH LC-cell 5510 could bemounted in the back of the rearview assembly so as to have its absorbingaxis be parallel to the transmitting axis of the second reflectivepolarizer of the switchable mirror 5214. As a result, the GH LC-cell5510 is enabled to operate as an opacifying means in areas of the mirrorwhere low transmission of light is required, thereby improving thecontrast between regions of the switchable mirror that are in the “hightransmittance” mode and those in the “low transmittance” mode. Suchimprovement is particularly relevant in a system employing an edge-litdisplay, which often would not have zero transmittance in the “off”state thereby leaking some light from a light source through the displaytowards the viewer.

It is appreciated that in applications requiring only a portion of thedisplay of the rearview assembly to be visible at any given time (e.g.,to activate a particular indicator), the use of the second GH LC-celldevice 5510 disposed at the back of the switchable mirror facilitatesblocking an undesired light transmission through selected areas of themirror thereby resulting in a more aesthetically pleasing product.

It is recognized that variation on embodiments of a SMS described hereincould be used not only in a rearview automotive assembly but also inwindows in architectural, transportation or aerospace applications.

Reduction of Double Imaging:

“Double imaging” is a familiar phenomenon arising from reflection oflight from several surfaces in a multi-surface structure and oftenreferred to as parallax. Multiple images formed in reflection frommultiple surfaces obscure the main image of interest and are mutuallyoffset, in the image plane, by distances that are dependent on thegeometry of the positioning of the multiple reflective surfaces and theoptical properties of the media involved. In the well-known example of amultiple reflection of the incident beam I of light from aplane-parallel optical plate, schematically illustrated in FIG. 56(B), atransverse offset Δa between the first and second order reflected beamsR₁ and R₂, respectively, is calculated according to Δa=d·tan(sin⁻¹(n₁sin θ_(I)/n_(G))), where d is the thickness of the plane-parallel plate,n_(I) and n_(G) are the refractive indices of the incident medium andthe material of the plate, respectively, and θ_(I) is the angle ofincidence. It is appreciated, therefore, that unless precautions aretaken, embodiments of a switchable mirror system of the invention thatincorporate two RPs may generate more than one image in reflection atleast because the two RPs are offset with respect to one another alongthe direction of incidence of ambient light and have similar reflectancecharacteristics. Moreover, the spurious reflections produced by otherreflecting surfaces will further camouflage the main image. It is alsoappreciated that formation of multiple images becomes particularlydetrimental to the user of the rearview assembly when the multipleimages have intensities that differ within several tens of percent orare substantially comparable.

For example, when the RPs of the embodiments of the invention areseparated by about 1.8 mm and viewed at an angle of about 25 degreesthen the resulting transverse offset between the two images formed inreflection from the RPs is about Δa=1 mm and this separation representsa limit that may be acceptable for automotive applications. Accordingly,embodiments of the invention are judiciously configured so as to assurethat the transverse offset between the two images formed in reflectionof ambient light in the RPs of the invention is less than 0.75 mm, morepreferably less than 0.50 mm, and most preferably less than 0.25 mm.

One approach to minimization of the double imaging is a reduction ofseparation distance between the reflecting surfaces at issue. In apractical embodiment of the SMS that contains a LC-cell-based device andtwo RPs such approach implies that the separation between the RPs shouldbe reduced. It is appreciated that, in general, the RPs used inembodiments of the SMS of the invention may be either APBF-based orwire-grid based. FIGS. 57 and 58 provide several examples, mostlyconcentrating on structures of the TN LC-cell that is part of the SMS ofthe invention. It will be appreciated that numerous components andelements of the rearview assembly incorporating embodiments of the SMSdiscussed in reference to FIGS. 57 and 58 are not shown in these figuresin order to simplify the illustration. The presence of such componentsand elements is known from other teachings of this application.

FIG. 57(A) illustrates an alternative embodiment of a SMS of theinvention that includes a switchable polarizer 5210 in front of aswitchable mirror 5710. The switchable mirror 5710 comprises a TNLC-cell formed by substrates 5712 and 5714 the inner surface of each ofwhich carries a multi-layer structure 5716. The cavity of the TN LC-cellis filled with the TN LC-medium 5717. As shown in partial view of FIG.57(B), an embodiment of the multi-layer structure 5716 is includes anAPBF 5718, a layer 5720 of TCO such as, e.g., ITO, an optionalpassivation layer 5722 (such as SiO₂ or Ta₂O₅), and an alignment layer5724 that is in physical contact with the LC-medium 5717. The remainingportion of the embodiment is structured as a mirror image of the portiondescribed. Another embodiment of the thin-film structure 5716′ is shownin partial view in FIG. 57(C) to contain a layer of wire-grid polarizer5730 overcoated with a planarization layer 5732 (to provide a flatsurface and a barrier between the wire-grid layer and the LC-medium5717), followed by a TCO layer 5720, an optional passivation layer 5722,and the alignment layer 5724. The remaining portion of the embodiment isstructured as a mirror image of the portion described. In bothembodiments of FIGS. 57(B) and 57(C), therefore, the reflectivepolarizers 5718 (or 5730) are incorporated within the TN LC cell 5710(i.e., disposed on the inner surfaces of the substrates of the TN LCcell), thereby reducing the separation distance between the reflectivepolarizers to that equal to the sum of thickness of a gap of the cell5710 and the thicknesses of all intermediately located layers. In atypical TN LC device, the LC-layer thickness is approximately 3 to 20um. The two RPs separated by such a distance would essentially appear asone reflective surface to the human eye. The 20 micron separationbetween the RPs would result in a transverse offset between doubleimages of only 0.012 mm, while the 3 micron case would have an imageseparation of 0.002 mm. In either of these cases the two images would beessentially coincident and perceived by the viewer as one.

It is appreciated that a combination of the wire-grid and APBF-based RPsmay also be employed in an embodiment of the invention, as shown in FIG.57(D). With respect to FIGS. 57 (B-D), if the thickness of the medium5717 is 50 microns then the separation between images formed inreflection from the two RPs of the LC cell 5710 would be about 0.029 mm,as calculated with the use of the above-referenced formula.

In another embodiment of the SMS of the invention employing two RPs, oneof the RPs may be disposed within the TN LC-cell of the embodiment whileanother is disposed outside of the cell. This structure is illustratedin an embodiment of FIG. 58, with the example of using wire-gridpolarizers 5730 and 5810 (although a similar embodiment with APBF-basedRPs is also within the scope of the invention). As shown, the rearpolarizer 5730 is disposed inside the TN LC-cell 5816 and the frontpolarizer 5810 is disposed on the outer surface of the substrate 5714 ofthe cell 5816. The separation between the reflective layers 5730 and5810 in this case is reduced to approximately the sum of thickness ofthe substrate 5714 and the LC-medium 5717. It is also appreciated that,in the embodiment of FIG. 58, the wire-grid polarizer 5730 is usedsimultaneously as the reflective polarizer and the electrode layer ofthe TN LC-cell 5816.

The wire-grid layer only has high conductivity in the direction of thewire Therefore, in any embodiment where the wire-grid polarizer is usedas an electrode, it may be necessary to supplement the conductivity witha TCO layer under or over the wire-grid layer. Such a TCO layer is shownin FIGS. 57(C, D) as 5724 and not shown in FIG. 58. Alternatively or inaddition, the wire grid pattern could contain a wire-to-wire conductivebridges to establish some conductivity perpendicular to the wiredirection.

As shown in examples of FIGS. 57(C, D) and 58, in embodiments employingwire-grid structures as RPs, a passivation layer and/or planarizationlayer of a polymer or metal oxide can be used to overcoat the wire-gridstructure to protect it from mechanical damage and corrosion. Due to itsdirectional structure, the wire-grid polarizer could also act as analignment layer for the LC-cell as the long axes of the LC mediummolecules will tend to align with wires. If alignment of the long axisof the liquid crystal molecules perpendicular to the grid is required,then a planarization layer may be necessary to flatten the structure ofthe wire-grid and to reduce its effect on orientation of the LC-mediummolecules. A TCO coating and/or a LC-medium alignment coating (such asrubbed polyimide or polyvinyl alcohol) can be applied on top of thewire-grid structure if desired. However, given the delicate nature ofthe wire-grid structure, non-contact methods for creating an LC-mediumalignment layer (such as angular deposition of SiOx or UV exposure ofthe alignment layer) may be preferred.

Overall, the APBF-based RPs used in embodiments of a SMS may includeDBEF-Q, APF-25, APF-35, APF-50 or other equivalent plastic-basedreflective polarizer materials. When the employed RP is APBF-based, itis preferably laminated to a corresponding substrate, using the methodof the invention discussed in reference to FIG. 3, in such a fashion asto satisfy distortion requirements of the automotive industry asdiscussed above. It is appreciated that, in the embodiments of the SMSof the invention, an APBF-based RP could be overcoated with a TCO, anoptional passivation layer, and a LC alignment film as discussed inreference to FIGS. 57,58. Moreover, the use of a plastic-basedreflective polarizer as substrate for the LC-cell based device is alsoinvisioned within the scope of the invention. An example of a LC-cell5900 configured according to this principle is shown in FIG. 59 andcould be compared with the device 3303 of FIG. 33(A).

Another approach to minimization of the spurious imaging is modificationof the substrates of an embodiment.

It is appreciated that, generally, the substrates of the SMS of theinvention could be made of glass or plastic materials. In addition, incertain embodiments it is advantageous for the substrate to preserve thepolarization states of reflected and transmitted light. In certainembodiments it is desirable for either the first or the second substrate(where the first substrate is one closest to the viewer) or both thefirst and second substrates to depolarize light. It is preferable tohave at least one or more substrates be less than 1.2 mm thick, morepreferable less than 0.75 mm thick and most preferably less than 0.5 mmthick. If, as an example, the RPs of the embodiment of FIG. 33(A) wereseparated but such distances, the transverse offset between the images,formed in reflection from the RPs 331, 3312 at a 25 degree viewingangle, of 0.77 mm, 0.44 mm and 0.29 mm, respectively, as calculated withthe above-referenced formula. The substrates could be processed asindividual cut-to-shape pieces, processed as an array in sheets or, ifthe substrates were thin enough, processed using a roll-to-roll process.

Using thinner substrates and/or reducing the number of substrates and/orusing transparent plastic substrates rather than glass substrates iscontemplated by the embodiments of the invention and will reduce theweight of the overall mirror system which is desirable in thetransportation and aeronautic applications. Reducing the thickness ofthe overall mirror system also allows for thinner, sleeker, and moreaesthetically pleasing mirror package designs.

As a baseline example, an SMS embodiment having two DBEF layers as RPsis configured according to the following sequence (when viewed from thefront of the mirror system):Glass/TCO/LC1/TCO/Glass/RP1/Glass/TCO/LC2/TCO/LC/Glass/RP2/Glass. Here,TCO represents a transparent conduction oxide or the like, LC1represents a guest-host LC medium or an orientated EC-medium, and RPrepresents an APBF. The LC-cells are preferably produced first and thenbonded/laminated to the RP material. In fabrication, the two LC-cellsare placed on either side of a first reflective polarizer RP1, thesecond reflective polarizer RP2 is disposed between the second LC-celland another lite of glass. The entire five-lite structure furtherundergoes a bonding/lamination process described in reference to FIG. 3to form the final assembly.

It is recognized that, in a specific embodiment, the number ofsubstrates used to configure the SMS of the invention may be reduced.For example, FIG. 60 illustrates a SMS embodiment 6000 in which the GHLC-cell 6004 and the TN LC-cell 6008 share a substrate 6010. As shown,the front RP 6014 is disposed within the GH LC-cell 6004 and outside theTN LC-cell 6008, while the rear RP 6018 is disposed within the TNLC-cell 6008. Transparent electrode layers 6020, 6022, 6024, and 6026are appropriately deposited on the internal surfaces of correspondingcells and/or corresponding APBFs to make the cells 6004 and 6008operational. Lamination of each of the APBFs 6014, 6018 to acorresponding substrate and lamination of the components comprising theembodiment 6000 is accomplished using the lamination method of theinvention as described herein. It is recognized that the front APBF 6014can be instead disposed on surface II. It is also appreciated that, inan alternative embodiment, a wire-grid polarizer (not shown) can beemployed in place of at least one of the APBFs 6014, 6018.

Depending on the quality of the glass, it may be necessary to have eachlite of glass be 1.6 mm thick or even thicker. (Thinner, less expensiveglass may have inadequate optical distortion properties, but its use isalso contemplated) The total mass of this construction then isapproximated as weight of a piece of glass having transverse dimensionsof a substrate and thickness of about 8 mm. Given the density of glassof about 2.44 grams/cm³, the preferred net weight of the embodiment perunit area is about 2.0 grams/cm². (The TCO and RP layers are relativelythin and can be ignored to the first order of magnitude). In someapplications the weight per unit area of 2.0 grams/cm2 may not beacceptable. For instance, in automotive rearview mirrors where themirror is suspended from the windshield, minimization of arisingvibrations of the mirror may dictate a reduction of its weight.Therefore, weight per unit area of the embodiments of the SMS of theinvention, regardless of the number of substrates used, is preferablyless than 2.0 g/cm2, more preferably less than 1.2 g/cm2, morepreferably less than 1.0 g/cm2 and most preferably less than 0.75 g/cm2.For instance, if 1.6 mm thick glass substrates are used in a structuredefined above, the weight per unit area of the SMS embodiment would beabout 1.17 g/cm2. If higher quality glass were used, the thickness ofthe lites could be reduced to 0.7 mm and the weight per unit area wouldbe approximately 0.51 g/cm2.

Minimization of Transmission in a “Low Transmission” Mode:

One possible shortcoming of a segmented switchable mirror systememploying RPs may stem from the fact that light from a display backlightor a backlight illuminator of such system may leak through the segmentsof the mirror that are not active at the moment. An example of suchsituation is provided by a rearview assembly employing a segmentedmirror system and a TFT-LCD, which is continuously illuminated but onlya portion of which has to be viewable at any given moment through acorresponding segment of the mirror (e.g., to provide visible readingsof a compass heading, time, or temperature to the viewer). One possiblesolution to the light-leakage problem and assuring that transmission ofthe segmented mirror system in “high R/low T” mode is minimized is theuse of RPs having high polarizing efficiency. For efficient use inrearview mirror assemblies the light leakage through the mirror systemoperating in the low-transmission state should be below 7%, preferablybelow 4%, and most preferably below 2% of the amount of incident light.The efficiency of a given polarizer can be determined by measuring thelight transmission through a combination of the given RP and anefficient absorptive polarizer. Table 2C shows the polarizingefficiencies for several types of polarizers based on measurements,while paired with an absorptive polarizer, in two configurations: a)transmission axes of the two polarizers are collinear; and b)transmission axes of the two polarizers are perpendicular.

TABLE 2C a) % T of light b) % T of light Absorptive Polarizer(transmission (transmission axes Polarizing Paired With: axes collinear)perpendicular) Efficiency Absorptive Polarizer 77.58 0.14 551 APF-50 (3MInc.) 88.91 2.40 37 APF-35 (3M Inc.) 89.97 3.23 28 DBEF-Q (3M Inc.)88.31 6.29 14 Wire-grid polarizer 89.23 0.39 230 (Moxtek)

In a segmented mirror system employing a TN LC-cell device and a pair ofRPs (see, e.g., embodiments of FIGS. 33, 34, 52-55), an alternativesolution to the above-described problem may be provided by having a dyeadded to the TN LC-medium in such a fashion as to have the absorptionaxis of the dye be collinear with the reflective axis of the RP locatedat the back of the TN LC-cell. In such configuration, the lighttransmitted from the backlight or display through the rear RP will beabsorbed by the dye.

Yet another solution to minimize the transmission of the mirror systemin a “high R/low T” mode of operation would be to add an absorptivepolarizer behind the front RP (relative to the viewer) such that theabsorption axis of the former is collinear with the reflection axis ofthe latter.

The same techniques used to enhance the viewing angle and contrast ratioof LCD's can be used to improve the performance of the LC switchablemirror element. The combination of liquid crystal fluid and element cellgap can be optimized for the best optical performance in the 1^(st),2^(nd), or 3^(rd) minima with a first minima device being preferred.Compensating films can be used to improve off angle performance such asuniaxial and biaxial oriented retardation films, coated liquid crystalfilms or modified TAC films. These films are available from Fujifilms(Wide View), Nippon Oil, Zeon Chemical, LG Chemical, JSR andKonica-Minolta.

Multiple Electrode Surface Multiple Electrode Segments Contact Methods:

In switchable mirror systems described in this specification there is asubstrate having electrodes with many segments and a substrate that canhave electrodes on one or both surfaces. Making reliable electricalcontact between these electrodes and a printed circuit board or driveelectronics is challenging. The substrates can be offset in an alternatepattern in either transverse direction with respect to a direction ofpropagation of light (i.e., along either x- or y-axis or along bothaxes) to expose the electrode surfaces and enable contact. If asubstrate has an electrode on both surfaces, or if two substrates thathave electrodes oriented back-to-back share the same offset, electricalcontact can be made to both electrodes with, for instance, a C-shapedclip. Alternatively, both electrodes could be patterned in analternating offset contact configuration so as to allow for the C-shapedclip to be set in contact with the top electrode, the bottom electrode,or both electrodes. In this way the top and bottom electrodes could beaddressed independently. If the top and bottom electrodes were segmentedand the multiple segments were offset relative to one another, thesegments could also be addressed independently. Contact can be made toelectrodes with offset substrates that form a contact ledge with amultiple contact spring connector inserted onto the contact ledge,multiple C shaped clips with a leg commonly called dual or single inline clips in the LCD industry, a C shaped buss clip with a solderedwire or spring connector, a heat or pressure bonded connection to aflexible circuit ribbon or a conductive elastomer type connector. Ifthere is no offset between the substrates a conductive material such asa coating or metal filled ink or adhesive could be applied such that itcontacts the electrode and rolls over onto perimeter edge of thesubstrate to allow that electrode connections could be made to the edgeof the substrate. Electrical connection to the conductive portion on theedge of the substrate could be made with a spring clip compressed by ormolded into a bezel assembly, a L shaped clip, a Z shaped clip or a Jshaped clip. One portion of the clip could be attached to the backsurface of the mirror assembly if desired. If the spacing between thesubstrates allows, part of a J shaped clip cold be inserted between thesubstrates to make contact to the electrode. Another method ofcontacting the electrode surface is to use wire bonding to connect theelectrode surface to a control module or electrical distribution system.

It is recognized that the configuration of the TN LC-cell (such as cell3303), which rotates the polarization of light by 90 degrees upontraversal of the powered “off” cell and which is used in conjunctionwith the two aligned RPs (such as RPs 3311, 3312), is intentionallychosen. The purpose of such configuration is to assure that in the caseof failure (power off) the switchable mirror system of any of theembodiments discussed in reference to FIGS. 33, 34, 45, 46, 52-59 thatemploy such a TN LC-cell in the rearview assembly remains in thereflecting state, and that the user is still able to such assembly as asimple rearview mirror. It is appreciated, however, that a similarperformance will be achieved if an alternative configuration werechosen, where the LC-medium does not rotate the polarization of lightupon traversal of the powered “off” LC-cell and where the LC-cell issandwiched between the two crossed RPs (not shown). This alternativeembodiment is also contemplated within the scope of the invention.

Moreover, it is desirable to have a failed (powered off) switchablemirror system have reflectance that meets or exceeds minimum reflectancestandards required by regulation (reflectance greater than 35% in the USand greater than 40% in Europe). When any embodiment of an SMS describedabove in reference to FIGS. 52 through 59 fails, it should haveintermediate (“mid R”) level of reflectance, as shown by “PowerOFF/Power OFF” line of Table 2B. It is desirable that various parametersand characteristics (such as dye concentration and properties,absorption and reflection of glass coatings and reflective polarizer) ofan embodiment of the SMS be judiciously chosen to meet minimumreflectance regulations in the “mid R” mode. If an orientated EC-elementthat absorbs one polarization of light is used in place of the GHLC-cell and such EC-element is designed to become transparent (bleached)with power “off”, the mirror system would fail in the high-reflectance(“high R”) mode, as shown by Power OFF/Power OFF” line of Table 2B1. Itis desirable that the mirror system meets or exceeds minimum reflectanceregulations in the “high R” state.

Embodiments of rearview assembly that combine means for recirculation oflight emitted by a backlight (emitter) to illuminate the LCD and anembodiment of the SMS of the invention are also within the scope of thepresent invention. Such embodiments include generally include more thantwo RPs, one of which is employed outside of the SMS. As shown in FIGS.61(A, B), for example, one such rearview assembly embodiment 6100contains the SMS (such as 5200, 5300, 5500, 5700, or 5900) and an LCD1850 that is illuminated with light emitted by a light emitter 1920. Asshown, an RP 1910 is used to optimize transmission of unpolarized lightfrom the light emitter 1920 through an LCD 1850 in a conventionaldisplay application by re-circulating a portion of the emitted lightbetween the RP 1910 and the reflector 1950. The RP 1910 and thereflector 1950 positioned on the opposite sides of the light emitter1920 in a fashion described in prior art. In a related embodiment 6120of FIG. 61(B), the RP 1910 is shown to be disposed between the LCD 1850and an embodiment of the switchable mirror system.

E) Exemplary Embodiments with Tailored Optical Characteristics.

The effect produced by a reflectance-enhancing coating on the overall(unpolarized light) reflectance and polarized transmittancecharacteristics of a mirror assembly may be quantified by defining afigure of merit such as, e.g., the ratio of the polarized transmittanceand the overall reflectance (PT/R). This figure of merit is listed inTable 3, together with the corresponding reflectance and transmittancedata discussed above with reference to embodiments of FIGS. 8(A-G). Inaddition, Table 3 contains the data representing performancecharacteristics associated with an embodiment similar to the embodiment836 of FIG. 8(D) but having the lite 826 removed. FIG. 10 presents thedata of Table 3 in a graphical form. In an attempt to optimize thestructure of an automotive mirror assembly (that comprises anAPBF-laminate and has a given overall, unpolarized light reflectancevalue) by achieving high polarized transmittance, variousreflectance-enhancing layers may be evaluated and those providing forhigher polarized-transmittance-to-overall-reflectance (PT/R) ratios maybe preferred. The choice of materials for an APBF may also be based onsimilar criteria. For example, in comparison with the PT/R ratio of 0.45for the prior art transflective mirror assembly embodiment 800, the PT/Rratio of the embodiments of the current invention (where the employedthin-films stacks may or may not include the reflectance-enhancinglayers) may be increased above 0.5 and preferably above 0.75. In aspecific embodiment, the PT/R ratio may be increased to above 1.0 andpreferably above 1.25.

TABLE 3 Light Increase of Throughput, PT, [times] Overall Overall[cd/m²] (in Reflectance Transmittance (from comparison R, [%] T, [%]Polarized Display of with (unpolarized (unpolarized Transmittance 8,000cd/m² embodiment Embodiment light) light) PT, [%] to Viewer) 800) PT/R800, FIG. 8(A) 55.0 32.4 32.4 2,592 1.0 0.59 828, FIG. 8(B) 51.1 46.588.5 7,080 3.5 1.73 830, FIG. 8(C) 50.2 47 89.5 7,163 3.6 1.78 836, FIG.8(D) 45.3 44 84.0 6,719 3.4 1.85 836 (with 45.6 43.3 81.8 6,542 3.3 1.79superstrate 826 removed) 844, FIG. 8(E) 50.6 37.5 74.2 5,933 3.0 1.47850, FIG. 8(F) 50.6 36.7 68.3 5,463 2.7 1.35 860, FIG. 8(G) 55.1 31.459.6 4,766 2.4 1.08

For example, applying quarter-wave dielectric coatings to at least oneof surfaces I and II in a mirror assembly embodiment that comprises anEC-element and a reflective polarizer (such as embodiments of FIG. 6 orFIG. 8(D)), potentially increase the overall reflectance of the mirror.The gain in reflectance, however, may come at the expense of somedisadvantages such as spurious reflections perceived as double-imagesand higher reflectance of the rearview mirror system in the “darkened”state. The “darkened” state corresponds to the situation when thetransmittance of the EC-element is minimized and interfaces behind theEC-medium do not meaningfully contribute to the overall reflectivity ofthe mirror assembly. Therefore, in one embodiment it may be preferred tohave surfaces I and II with low reflectivity values. If the reflectivityof at least one of surfaces I and II is minimized, then in the darkenedstate the overall reflectivity of the described mirror assembly is alsominimized as the overall reflectivity is predominantly defined, in thedarkened state, by reflectance values of surfaces I and II. As a result,the dynamic range of the reflectance of the mirror assembly may bebroadened. The reflectivity of surface II may be reduced, for example,by depositing a half-wave thin-film layer on surface II. On the otherhand, in another embodiment, it may be desirable to increase the valueof overall reflectance that the mirror has in the darkened state. Forexample, some automotive manufacturers prefer that the minimumreflectance of convex or aspheric outside EC-mirrors be above twelvepercent. An appropriate adjustment of the overall minimum reflectancevalue can be achieved by disposing a reflectance-enhancing coating infront of the EC-layer (with respect to the viewer), e.g., on surface Ior surface II, instead of disposing such a coating behind the EC-layer.Other methods such as adjusting the cell spacing of the EC-element orthe concentrations of the anode and cathode materials, or the variationof the operating voltage may also be used to adjust the minimumreflectance of the device.

The reflectance of a surface overcoated with a single dielectricoverlayer can also be enhanced by adding a pair of layers to the singledielectric overlayer. The refractive index of one such layer, designatedas low (or L), should be smaller than the refractive index of the singledielectric overlayer, while the index of the second layer, designatedhigh (or H), should be larger than the refractive index of the L layer.The H layer may be made of the same material as the single dielectricoverlayer, or it may be made of a different material. The degree towhich the overall reflectance of an optical surface is enhanced dependson the index contrast of the thin-film materials used for suchenhancement. The equivalent optical thickness of each of the H and Llayers in the enhancing pair of layers should be about a quarter-wave soas to maximize the resulting reflectance of the thin-film stack.Preferably, in such a pair of layers, the refractive index of thereflectance-enhancing layer with the “high index” value is greater thanabout 1.7, and more preferably greater than 2.0. In some embodiments,such index may be on the order of or even exceed 2.4. Preferably, thedifference between indices of the H and L layers should be greater thanabout 0.4 and more preferably greater than about 0.7. In someembodiments, the index of L-layer may be more than 1.0 below that ofH-layer. Additional high/low pairs can be added to further enhance thereflectance. For instance, the overall material stack may comprise(starting with materials farthest from viewer) G/RP/H/G.

Alternative embodiments of the structures having enhanced reflectance,for use in automotive mirror assemblies may be, e.g., G/RP/H/L/H/G, orG/RP/H/L/H/G/ITO/EC/ITO/G and similar structures, where, instead of alayer of the ITO on surface Ill, a semi-transparent layer of metal(preferably Ag or Ag-based alloy such as silver-gold alloy, which isknown to be chemically stable when in contact with most fluid-based ECmedia) may be used for enhancement of reflectance. Additional layers maybe employed to attain color neutrality in reflection, as discussed invarious commonly-assigned patent applications. In the abovementionedstructures, G denotes a glass layer (substrate); RP corresponds to areflective polarizer component; H and L conventionally denote dielectriclayers with high and low refractive indices, respectively; and ECsymbolizes a layer of electrochromic medium. The H and L layers or anycombination of such layers may be deposited directly onto the glasssubstrate or, alternatively, may be disposed directly onto thereflective polarizer component, depending on the requirements of a givenapplication. The refractive index of any bulk layer interface in thereflective polarizer system can also play a role in modifying,attenuating or enhancing the reflectance. In general, to enhancereflectance a larger difference in refractive index between twoneighboring materials is preferred. Conversely, minimizing thedifference in the refractive index between neighboring materialstypically will reduce the reflectance. Any additional interfacematerials present on the reflective polarizer can influence thereflectance due to the refractive index mismatch phenomena.

If an additional depolarizer (in the form of a depolarizing layer, forexample), or pressure sensitive adhesive or other material is placedbetween the reflective polarizer and a coated or uncoated glass surfacethen the refractive index of this material will be a determining factorin the final reflectance. For example, in one embodiment, when ahigh-index reflectance-enhancing layer is present on surface IV of thesystem, the system reflectance may be maximized if the neighboringmaterial has a relatively low refractive index—the lower the better. Itis understood that optimization of the entire system is required toachieve a desired set of properties. The optimal refractive indices ofmaterials used will generally depend on the indices of surroundingmaterials and may vary depending on the application.

In other possible embodiments, as discussed below, the use of a gradedindex material between the reflective polarizer and the adjacent glasssurface may result in the optimal reflectance effects if the there aredivergent requirements for the reflective polarizer and the coated oruncoated neighboring surface or interface. Non-limiting examples ofsuitable high refractive index layers are: antimony trioxide, cadmiumsulfide, cerium oxide, tin oxide, zinc oxide, titanium dioxide orvarious titanium oxides, lanthanum oxide, lead chloride, praseodymiumoxide, scandium oxide, silicon, tantalum pentoxide, thallium chloride,thorium oxide, yttrium oxide, zinc sulfide, zirconium oxide, zinc tinoxide, silicon nitride, indium oxide, molybdenum oxide, tungsten oxide,vanadium oxide, barium titanate, hafnium oxide, niobium oxide, andstrontium titanate. Non-limiting examples of suitable low refractiveindex layers are: aluminum fluoride, aluminum oxide, silicon oxide,silicon dioxide, calcium fluoride, cerium fluoride, lanthanum fluoride,lead fluoride, lithium fluoride, magnesium fluoride, magnesium oxide,neodymium fluoride, sodium fluoride, thorium fluoride or a porous filmwith high density of voids. The reflectance value of the mirror systemand spectral properties of light reflected by the system can be furthertuned by using at least one optical layer having material propertiesthat vary with layer thickness. A common example of such materiallynon-uniform layer is known as a graded composition coating (GCC). Incomparison with the graded thickness layers (characterized by spatiallyuniform material properties and spatially non-uniform thickness), a GCCmay have a spatially non-uniform material composition resulting, e.g.,in a refractive index that varies as a function of thickness. In oneembodiment, the mirror assembly may include a GCC formed with a variablemixture of SiO₂ (refractive index of about 1.45) and TiO₂ (refractiveindex of about 2.4). For example, next to a substrate onto which the GCCis deposited, the GCC may predominantly contain SiO₂ (and, therefore,have a refractive index approaching 1.45). Throughout the thickness ofthe GCC, the material composition of the GCC is varied to increase thecontent of TiO₂. As a result, the refractive index of the outer portionof the GCC may be approaching 2.4.

Alternatively or in addition, the overall reflectance of the rearviewmirror assembly containing a multi-layered RP may be increased byaltering the layers of the RP component. This may be accomplished, e.g.,by adjusting thicknesses of different layers in a multilayeredplastic-film based reflective polarizer. Alternately, the indices ofthese layers may be altered. The net reflectance and transmittance maythus be adjusted or tuned to the needs of a given application. In antypical inside rearview automotive mirror the reflectance is preferablygreater than about 45%, more preferably greater than 55%, even morepreferably greater than 60% and most preferably greater than about 65%.

The spectrum of light reflected (and that of light transmitted) by anembodiment of the mirror system of the invention can be tuned ormodified by adjusting the thickness of the reflectance-enhancing layers.The peak reflectance will vary with optical design wavelength and thiswill result in a change in color gamut of the reflected (andtransmitted) light. In discussing color distributions (i.e., spectra oflight), it is useful to refer to the Commission Internationale deI'Eclairage's (CIE) 1976 CIELAB Chromaticity Diagram (commonly referredto the L*a*b* chart or quantification scheme). The technology of coloris relatively complex, but a fairly comprehensive discussion is given byF. W. Billmeyer and M. Saltzman in Principles of Color Technology,2^(nd) Edition, J. Wiley and Sons Inc. (1981). The present disclosure,as it relates to color technology and uses appropriate terminology,generally follows that discussion. According to the L*a*b*quantification scheme, L* represents brightness, a* is a colorcoordinate that denotes the color gamut ranging from red (positive a*)to green (negative a*), and b* is a color coordinate that denotes thecolor gamut ranging from yellow and blue (positive and negative valuesof b*, respectively). As used in this application, Y (sometimes alsoreferred to as Cap Y), represents the overall reflectance. For example,absorption spectra of an electrochromic medium, as measured at anyparticular voltage applied to the medium, may be converted to athree-number designation corresponding to a set of L*a*b* values. Tocalculate a set of color coordinates, such as L*a*b* values, from thespectral transmission or reflectance, two additional parameters arerequired. One is the spectral power distribution of the source orilluminant. The present disclosure uses CIE Standard Illuminant A tosimulate light from automobile headlamps and uses CIE StandardIlluminant D₆₅ to simulate daylight. The second parameter is thespectral response of the observer. Many of the examples below refer to avalue Y from the 1931 CIE Standard since it corresponds more closely tothe spectral reflectance than L*. The value of“color magnitude”, or C*,is defined as C*=√{square root over ((a*)²+(b*)²)} and provides ameasure for quantifying color neutrality. The metric of “colordifference”, or ΔC* is defined as ΔC*=√{square root over((a*−a*′)²+(b*−b*′)²)}, where (a*, b*) and (a*′,b*′) describe color oflight obtained in two different measurements. Additional CIELAB metricis defined as ΔE*=(Δa*+Δb*²+ΔL*²)^(1/2). The color values describedherein are based, unless stated otherwise, on the CIE Standard D65illuminant and the 10-degree observer.

Table 4 illustrates the calculated changes in spectral distribution oflight reflected by the embodiment of FIG. 8(D) that was modified byadding (depositing) a single layer of titania, TiO₂, on surface IV. Inthis calculation the refractive index of TiO₂ layer was assumed to equaln=2.24 (with recognition that in practice this index may somewhat varydue to processing conditions). In comparison, Table 5 similarlyillustrates changes in spectral distribution of ambient light reflectedby the embodiment of FIG. 8(D) that was modified by deposition of anadditional H/L/H stack on surface IV. In this calculation it is assumedthat the high index layer has a refractive index of 2.24 and the lowindex layer has a refractive index of 1.45. The thin film modelsdescribed above were used for both of these calculations. In bothexamples (the one of Table 4 and the one of Table 5) all quarter-wavelayer thicknesses are adjusted to the same design wavelength. As shownin Table 4, the reflectance reaches its peak value at a designwavelength of about 550 nm. The color gamut of the reflected lightshifts towards blue (which is indicated by lower values of b*) when thedesign wavelength drops below approximately 450 nm, and towardsyellow/red for design wavelengths of about 500 nm and above (which isindicated by increase of b* and a*). This effect is achieved due topreferential enhancement of the reflectance of the assembly in certainportions of the visible spectrum. As can be seen from comparison ofTables 4 and 5, the additional layers magnify the changes in reflectancespectrum, which is indicated by changes, in a* and b* values, thatincreases with changes to the optical thickness of the stack.Appropriate adjustment of optical thicknesses, refractive indices,and/or the number of layers in the stack independently may lead to aparticular spectral distribution of reflectance, as may be required by aspecific application of the mirror assembly. For instance, a givenreflectance with a yellow hue may be obtained or a different reflectancewith a blue or red hue may be obtained by the appropriate tuning of thelayer thicknesses.

TABLE 4 Reference Wavelength, nm Cap Y a* b* RP alone 47.18 2.95 −3.61400 49.43 2.03 −3.8 450 49.78 1.88 −3.57 500 49.97 1.81 −3.26 550 50 1.8−2.91 600 49.9 1.87 −2.56 650 49.67 2.02 −2.27 700 49.35 2.25 −2.1 75048.96 2.55 −2.1

TABLE 5 Reference Wavelength, nm Cap Y a* b* RP alone 47.18 2.95 −3.61400 51.79 0.51 −7.51 450 55.13 −1.47 −5.46 500 57.36 −2.36 −2.16 55057.91 −2.12 1.42 600 56.78 −0.5 3.74 650 54.41 2.37 3.32 700 51.62 50.85 750 49.35 5.71 −1.56

(E.1) Employment of UV-Protection Means

Plastic films having little absorption in the visible portion of thespectrum and, in particular, polymer-based RP films employed inembodiments of the present invention may be susceptible to degradationupon exposure to UV and/or short-wavelength visible light. Similarly, inembodiments of the invention that include LC-cell based devices,LC-medium may be similarly vulnerable. Protection of the APBFs andLC-cells from such degradation may be required and may be achieved in anumber of ways. Possible ways of UV-protection are discussed below withrespect to APBFs, but are understood to equally apply to UV-protectionof the LC-cell-based devices contained within the embodiments of theinvention.

For example, using protecting components that facilitate reflectionand/or absorption of UV-light either within or in front of the APBF willgenerally diminish the degree of degradation of the APBF. However,improvements in UV-stability of the APBF should be carefully weighedagainst possible changes in other system characteristics. For example,changing the composition of glass substrates or a laminate stack inorder to improve UV-stability of the APBF-containing mirror system mayreduce the overall durability of the system as measured by one of thetests discussed above. Optical distortions, haze, optical angularsensitivity, depolarization effects, color characteristics (especially,yellowish hue) of the system are but only several examples of parametersthat need to be considered while improving UV-light durability of thesystem. The use of UV-agents in the system could also affect the colorof an RGB display of the system, as perceived by the viewer, if suchUV-attenuators alter the transmission of the system in the visiblerange. (In this respect, the use of an RGB display that emits lightwithin very narrow bandwidths around the chosen red, blue, and greenwavelengths of operation may be preferred because in such a case theUV-agents protecting the APBF are less likely to interfere with lightemanating from the display.) Incorporation of UV-agents may also affectthe ability of a given component to withstand the fabrication processand its resulting mechanical characteristics (e.g., pliability andinclusions of particles). For example, UV-protection means used on thefirst surface of the mirror system may affect susceptibility toscratches, solvent resistance, as well as hazing or fogging of thatsurface. Finally, cost-efficiency of employed UV-protection andcommercial availability of UV-agents and methods of UV-protectionpresent an additional factor. Some issues of attenuation of UV-lightwithin a range of wavelengths of particular sensitivity to some types ofreflective polarizing films (e.g., wavelengths below 380 nm) and relatedtest methods are discussed in U.S. Pat. Nos. 7,557,989 and 7,124,651 anda U.S. Patent Application No. 2009/0262422, assigned to 3M, Inc. U.S.Patent Application No. 2004/0241469 discusses, for example, protectionof polyethylene napthalate articles from UV exposure and other externalinfluences. Disclosure of each of the abovementioned patent documents isincorporated herein by reference in its entirety. In the art ofautomotive mirrors, discussions of light exposure and related tests andpass/fail criteria can be found in SAE J1960 and SAE J1885, which areweathering methods defined by Society of Automotive Engineers. Inparticular, acceptable exposure of an inside rearview mirror per SAEJ1885 to radiation emitted by a xenon arc light source can be as high as600 kJ/m² or even 800 kJ/m², with a resulting color change of ΔE*<3measured in reflectance. Other cosmetic requirements may also apply suchas uniformity of fading of color, or yellowing, or haziness that mightoccur during testing. Additional methods on material testing solutionsis provided by Atlas material Testing Technology LLC and may be found athttp://www.atlas-mts.com/en/client_education/client_education_event_overview/weatherometer_workshops/index.shtml.

Several technologies that may be useful for light attenuation to protectthe reflective polarizer in various embodiments of the invention.Embodiments of the present invention may employ, for example, vacuumsputtered or sol-gel interferential coatings on one of the surfaces infront of the APBF as viewed by the observer. Some embodiments of thesetechniques are described in U.S. Patent Application No. 2002/0122962 andU.S. Pat. Nos. 5,332,618 and 7,153,578. Examples of applicable sol-gelcoatings are taught, for example, in U.S. Pat. Nos. 5,371,138 and7,288,283. Disclosure of each of the abovementioned patent documents isincorporated herein by reference in its entirety. By way of exampleonly, such coatings may be used on surfaces I, II, III, and IV of theembodiment 838 of FIG. 8(D) or on first and second surfaces of theembodiments of FIGS. 32(A-C).

In addition or alternatively, material composition of any substrate inembodiments of the invention may be modified as described, e.g., in U.S.Pat. Nos. 5,350,972 and 7,435,696, the disclosure of each of which isincorporated herein by reference in its entirety. It is understood thatonly those lites with modified material composition that are located infront of the APBF as viewed by the outside observer will produce thedesired result of protecting the APBF from UV-component of the ambientlight. In a specific embodiment, a particular substrate may include morethan one component or plate one of which is made of material containinga UV-agent. For example, in reference to the embodiment 404 of FIG.4(B), a prism element 408 may contain a UV-absorbing agent while thematerial of the plate 308 may be made of conventionally used glass. Insuch a case, however, the concentration of the UV-agent across the prismmay be appropriately graded to achieve spatially uniform opticalcharacteristics of the embodiment. A preferred alternative solution maybe to add a UV-agent to a plane-parallel plate 308 instead and use theprism 408 made of conventional glass.

In embodiments where the APBF is located behind an electro-optic cellsuch as an EC-element or a cholesteric element, it is possible todispose the UV-attenuating agents within the electro-optics cell. Inreference to FIGS. 8(D-G), for example, a UV-attenuating agent may beadded within the cell 840. Cholesteric devices and EC-elements includingsuch UV-agents are disclosed in commonly assigned U.S. Pat. Nos.5,798,057, 5,336,448, 7,265,888, and 6,614,578, the disclosure of eachof which is incorporated herein by reference in its entirety.

Adhesive films such as PSAs and UV-curable adhesive and PVB that areused in a mirror system at locations in front of an APBF may alsocontain UV-absorbing agents. Although not necessary, the layers of theseadhesives and PVB may be as thick as a few mils. Auxiliary polymericfilms, such as those utilized to minimize UV-light transmission throughresidential or commercial windows may be laminated or co-laminated intoan embodiment of the invention. For example, a subdivision of a prismmirror element into a wedge and a flat piece with a PVB adhesive layeris disclosed in U.S. Pat. Nos. 4,902,108 and 5,481,395. In a specificembodiment, such UV-blocking films may be employed as cladding layer(s)during the manufacture of a multilayered ABPF itself. Such a filmproduct may have the benefit of both selective light attenuation anddepolarization. It is understood that several different methods of lightattenuation may be combined in order to produce desired results.

(E.2) Angularly Misaligned Reflective Polarizers

Adjustment of the overall reflectance in embodiments of the presentinvention may be carried out by employing laminates containing more thanone APBF elements. For example, embodiments of laminates of theinvention characterized in Table 6 were structured as[Glass/RP/RP/Glass]. FIG. 25 schematically illustrates this structure inexploded view, where two DBEF-Q films 2510, 2520 used as RPs aresandwiched between the glass substrates 2530, 2540. The APBF 2510 isoriented so as to have its polarization axis 2530 be collinear with thepolarization of the LCD (not shown) output, indicated in the table as“s-pol” which corresponds to the x-axis. Polarization axis 2560 of theadjacent DBEF-Q film 2520 is rotated with respect to the axis 2530 in anxy-plane, which is parallel to the films, by an amount indicated in thecolumn “Trial”. The data of Table 6 are shown for a D65 illuminant 10degree observer. Unless indicated otherwise, the data are notpolarization specific. The measurement data demonstrates that, bycombining a plurality of angularly misaligned reflective polarizers inan embodiment of the invention, a decrease in transmission of light fromthe display may be traded-off for an increase in the overall reflectanceof the embodiment. It shall be realized that, in practice, additionaloptical layers may be disposed adjacent to at least one of the pluralityof APBFs. Some embodiments employing a plurality of APBFs, such as thosedescribed in Table 6 or the like, may require that light transmittedfrom the display to the observer be color neutral. This situation mayarise in embodiments employing a reverse camera display (RCD). Therequired color neutrality may be achieved by adjusting a displayalgorithm for more accurate color rendering. In some embodiments, theadjustments of the display algorithm may allow for compensation of thecolor induced transmission bias from electrochromic medium or othercomponents.

Some applications may require a neutral spectral distribution ofreflectance of the mirror assembly (such distribution may, for example,lack high purity hues). In one embodiment of the current invention thecolor magnitude C* may be smaller than about 15. In a relatedembodiment, the color magnitude may be smaller than about 10, and, in aspecific embodiment, it may be most preferably less than about 5.

TABLE 6 Figure In Reflection In Transmission Transmittance % of Merit,Trial Y a* b* Y a* b* Absorbance % p-pol s-pol PT/R  0 deg 51.38 −0.52−0.39 45.7 −0.23 1.68 2.95 0.85 88.95 1.73 15 deg 55.99 −0.84 −0.96 42.90.05 2.29 1.07 1.42 76.96 1.37 30 deg 59.81 −0.73 −1.02 39.6 −0.04 2.570.61 2.31 71.64 1.20 45 deg 65.33 −1.29 −1.52 33.1 0.84 3.43 1.62 2.7352.36 0.80 60 deg 74.91 −1.20 −1.50 20.4 1.30 5.70 4.66 4.17 31.00 0.4175 deg 84.11 −2.40 −2.29 11.1 6.99 13.20 4.78 5.15 8.20 0.10 90 deg88.53 −1.95 −2.16 6.3 8.43 22.56 5.21 5.91 5.57 0.06

(E.3.) Embodiments Employing Opacifying and Reflectance-Enhancing Layers

In some embodiments, the area of the display may be smaller than thearea of the mirror element. Such embodiments are illustrated, forexample, in FIG. 8 (A, C-F, H) or in FIG. 6. The relatively hightransmittance of the reflective polarizer would generally make othercomponents in the mirror assembly to be visible to the viewer. Topreserve high polarized transmittance values of the RP component whilesimultaneously concealing these other components in the system (e.g., inthe outer areas 644 of FIG. 6), opacification may be employed. Practicalmeans of such opacification may include, but not be limited to, additionof an opaque material such as of plastic, or a layer of paint or ink, ora thin-film coating, suitably applied to an element of the mirrorassembly, across a rearward surface of the system relative to thereflective polarizer. Depending on an embodiment of the EC-mirrorassembly, such opacification may be carried out on surfaces III, IV, Vor VI. In embodiments containing a prism-based mirror (such as, e.g.,embodiments of FIGS. 4(B-D), 4(F) and 4(G)), the opacification may becarried out on surfaces II, III, or IV. Although embodiments of thepresent invention describe specific mirror systems having up to 3 litesof glass (or other material), additional lites may be used withoutlimitation as needed to meet requirements for the system. If additionallites are employed, an opacification layer may be placed on one or moreappropriate surfaces located behind the reflective polarizer relative tothe viewer, which may result is aesthetically pleasing appearance of theoverall rearview mirror assembly. The opacification means could bepresent across the entire area outside of the display or only inselected locations, as needed.

In addition, as discussed below, in a specific embodiment of theinvention, at least some edges of the opacified areas around theperimeter of the display region may be formatted to gradually vary thetransmittance of the mirror across its surface from fully transparent tofully opaque (and to accordingly gradually vary the reflectance of themirror across its surface). Literature provides some solutions foraesthetic gradual transitions from a display area to adjacent areas havebeen discussed in the literature. For example, in the area of therearview automotive mirrors the need for good match in color andreflectance has been recognized and thin-film coating-based solutionshave been proposed in, e.g., commonly assigned U.S. patent applicationSer. Nos. 11/713,849, 12/138,206, and 12/370,909, the disclosure of eachof which is incorporated herein by reference in its entirety. Agraded-thickness coating has been used in front of an APBF in, e.g.,U.S. Patent Publication 2006/0164725 as a means of gradual variation ofreflectance across the surface of a conventional viewing mirroremploying a display. The same publication discussed additional means ofhiding the edges of the display area in conventional viewing mirrors byadding a supplementary coated substrate, having a relatively highreflectance and low transmittance, in front of the APBF. Although thesolution provided in U.S. 2006/0164725 facilitates concealing the edgesof the display area, it suffers from the effect of parallax, whereby thespurious images are formed in reflection from the viewing mirror.Additional disadvantages of this solution stem from reduction inbrightness and contrast of the display, now perceived by the viewerthrough the viewing mirror and the supplementary substrate. Overall,solutions proposed in prior art were recognized to be inapplicable tothe field of automotive mirrors. The trade-off between a clearlydiscernable edge of the aperture or a parallax condition is generallyrecognized and no viable solution which avoids parallax and has astealthy edge at the display area of the mirror has been realized sofar. Other prior art means to adjust the reflectance (such as changingthe density of reflective particles contained within a coating placed infront of the RP included in the mirror system) may result in varyinghaze levels (scattering from agglomerated particles within the coating)and make the edges of the aperture noticeable. In an embodiment of thepresent invention, the reflectance may be varied from specular tonon-specular or the intensity of light reflected from the mirror may bevaried or graded along the edge of the opacified area. In an embodimentof the APBF-containing rearview mirror of the present invention,depending on the size and location of the display, it may be preferredto grade either some or all of the edges of the opacified areas aroundthe display region. The required gradations of transmittance orreflectance may be implemented by, for example, either spatiallymodifying the transmittance of the opacifying material itself or bypatterning such material in a spatially non-uniform fashion. Suchgradations may be implemented in various ways such as those described ina commonly assigned U.S. patent application Ser. No. 12/370,909. In aspecific embodiment such pattern may comprise, for example, a pattern ofdots created with varying spatial density. FIGS. 17(A) and 17(B)demonstrate front views of opacifying layers with graded edgesspecifically configured in a tapered fashion and a feathered fashion,respectively.

Structurally, embodiments of the mirror system of the inventioncontaining graded-thickness opacifying layers (also referred to asopacifying layers having a gradually changing thickness) may differ. Forexample, in an exemplary EC-type embodiment 884 of the invention,schematically shown in FIG. 8(I), a mirror system may be structuredsimilarly to that of FIG. 8(F) but additionally have a graded-thicknessopacifying layer 886 made of metal (such as Cr, Al, Ag or Ag alloy, Rh,Pd, Au, Ru, Stainless Steel, Pt, Ir, Mo, W, Ti, Cd, Co, Cu, Fe, Mg, Os,Sn, W, Zn or alloys, mixtures or combinations of the above) that isdisposed on surface V of the mirror system. It would be realized that,generally, the reflectance-enhancement layer 846 added between thesurface V and the graded-thickness opacifying layer 886, is optional. Asshown, all the perimeter of a window 888 in the layer 886 has gradededges. The thickness of the layer 886 varies across the plane of themirror (i.e., in xy-plane) between essentially zero and the maximumthickness (e.g., 500 Å). For comparison, FIG. 17(C) shows a front viewof another embodiment 1710 of a graded opacifying layer that is limitedwith graded edges only along the length of the mirror (x-axis, asshown). In a second dimension (y-axis), a window 1720 in the gradedlayer 1710 extends to the very edge of the mirror itself. Grading of thethickness of opacifying layer 1710 along the length of the mirror, asmeasured, is clearly seen from FIG. 17(D). The purpose of grading thethickness of the edges is to make the transition between the display andopaque regions less noticeable to the viewer. Such gradual opacificationor reflectance modification approaches may allow one to minimize thevisibility of the features behind the mirror in diffuse lightingconditions. This approach thus improves the aesthetics of the mirrorassembly regardless of whether a laminate, comprising a reflectivepolarizer such as the APBF, is a part of such assembly or not, and it isapplicable in various other types of mirrors (e.g., electrochromic,simple reflectors such as or simple tilt-prism mirrors, or other mirrorssuitable for use in automotive applications). Positioning of theopacifying layer, such as the layer 886, behind the RP 824 in anembodiment of the rearview mirror of the present invention facilitates asolution of problems acknowledged in prior art. In particular, suchorientation of the components in the mirror system allows for reductionof the visibility of the edges of the opening 888 in the graded-edgeopacifying layer without either the accompanying parallax effect orreduction in brightness and contrast of the display observed by theviewer 115.

Grading the edges of an opacifying layer as described above effectuatesacceptable aesthetics of the mirror system due to the gradual transitionbetween the transflective and opaque zones of the system. Hard-edged(abrupt) transitions between the zones of a multi-zone mirror system canalso be used, provided that an adequate match of reflectance andreflected color is maintained between the zones as perceived by theviewer. Several additional examples of implementation of hard-edgedtransitions in embodiments of the invention are discussed further inreference to FIGS. 35 and 36.

FIG. 35 illustrates an example of embodiment 3500 employing a multi-zonemirror system 3502 that includes an EC-element 840, containing two litesof glass 610 and 635, and a hard-edged OREL 3504. The Chromium300-Angstrom-thick OREL 3504 is disposed on the rear surface of theEC-element, surface IV, outside of the transflective zone 3510 of theembodiment 3500. An additional, third lite of glass 3512 is used forlamination of the APBF 824 between the lite 3512 and the EC-element 840.As shown, the APBF 824 extends over the transflective zone 3510 thatcorresponds to the display 1850 (not shown) but does not overlap anopaque zone 3514. Prior to lamination, a quarter-wavereflection-enhancing layer 3516 of TiO₂ (618 Å) is disposed on surfaceIV within the transflective zone 3510. Parameters of the EC-element 840have been described elsewhere in this application. Opticalcharacteristics of this embodiment are as follows: reflectance of thetransflective zone is 51.4%, a value of a* in reflectance is of −1.9,and a value of b* in reflectance is −2.5. The opaque zone has areflectance of 51.0%, a value of a* in reflectance is −3.1 and a valueof b* in reflectance is −2.6.

In further reference to the structure of FIG. 35, in an alternativespecific embodiment (not shown) a H/L/H quarter-wave stack 3516 of TiO₂(523 Å)/SiO₂ (876 Å)/TiO₂ (523 Å) may be placed between APBF 824 andsurface IV an alternative to a single quarter-wave layer of TiO₂. Tomatch the optical characteristics of thus configured transflective zone3510, an OREL 3504 is also modified to include a stack of Chromium (200Å) and Aluminum (80 Å) layers deposited in that order, in the opaquezone, on surface IV. This combination of components results in thetransflective zone having a reflectance of 64.1%, a reflected a* valueof −6.4 and a reflected b* value of −1.0. The opaque zone has areflectance of 64.0%, a reflected a* value of −3.7 and a b* value of−0.3.

In reference to FIG. 36, an embodiment 3600 of a multi-zone mirrorsystem 3602 employs a reflectance-enhancing quarter-wave layer 3604 ofTiO₂ (646 Å) on Surface V in the transflective zone 3510 and a Chromium(250 Å) OREL 3608 located on Surface IV in the opaque zones. In thisembodiment, the APBF layer 824 is spatially limited to the transflectivezone 3510 and is laminated between the third lite 3512 and theEC-element 840. Other system characteristics are the same as those ofthe embodiment 3500 of FIG. 35. The resulting optical characteristicsare as follows: a) Transflective zone 3510: reflectance of 51.3%, areflected a* value of −1.8 and a reflected b* value of −1.8. b) Opaquezone 3514: reflectance of 51.0%, a reflected a* value of −2.8 and areflected b* value of −2.2.

It should be noted that, in specific embodiments, thereflectance-enhancement coating may be configured so as to include aquarter-wave stack of thin-film layers such as titania (TiO₂) and silica(SiO₂), for example. Table 6A below provides some examples ofimplementation of the reflectance-enhancement coating 846 in embodimentsof FIGS. 8(E-G) containing an EC-mirror element. Table 6B illustratesimplementations of the reflectance-enhancement coating in embodiments ofFIGS. 32(A-C) that employ a prism-mirror element. Embodiments 3200 ofFIG. 32(A), 3210 of FIG. 32(B), and 3220 of FIG. 32(C) are structurallysimilar to the embodiment 410 of FIG. 4(C) in that in any of theseembodiments the APBF layer 302 is laminated between the prism 408 andthe glass plate 304. As shown in these embodiments, areflectance-enhancement stack 3202 is disposed on the rear, with respectto the viewer 115, surface of the prism 408 (surface II) prior to thelamination of the APBF 302; a reflectance-enhancement stack 3212 isdisposed on the front, with respect to the observer, surface of theglass plate 304 (surface III) prior to the lamination of the APBF 302;and a reflectance-enhancement stack 3222 is disposed onto the rearsurface of the embodiment (surface IV) either prior to or following thelamination of the APBF 302. Accordingly, embodiments of a mirror systemof a rearview mirror assembly that have an overall reflectance of theambient light in excess of 35%, or more than 400/%, more preferably morethan 50%, or even more than 60%, or more than 70%, and even morepreferably more than 75% are within the scope of the present invention.

TABLE 6A Reflectance- Display Enhancement Transmit- Transmit- EmbodimentCoating, 846 Reflectance tance tance (PT) 844 (FIG. 8E) TiO₂ 52.3 nm50.5% 34.9% 64.1% 844 (FIG. 8E) TiO₂ 52.3 nm 63.0% 21.5% 37.8% SiO₂ 87.6nm TiO₂ 52.3 nm 844 (FIG. 8E) TiO₂ 52.3 nm 72.0% 12.0% 19.8% SiO₂ 87.6nm TiO₂ 52.3 nm SiO₂ 87.6 nm TiO₂ 52.3 nm 850 (FIG. 8F) TiO₂ 52.3 nm50.4% 34.9% 64.1% 850 (FIG. 8F) TiO₂ 52.3 nm 62.6% 21.5% 37.8% SiO₂ 87.6nm TiO₂ 52.3 nm 850 (FIG. 8F) TiO₂ 52.3 nm 71.2% 12.0% 19.8% SiO₂ 87.6nm TiO₂ 52.3 nm SiO₂ 87.6 nm TiO₂ 52.3 nm 860 (FIG. 8G) TiO₂ 52.3 nm54.7% 29.9% 54.4% 860 (FIG. 8G) TiO₂ 52.3 nm 66.2% 16.8% 28.8% SiO₂ 87.6nm TiO₂ 52.3 nm 860 (FIG. 8G) TiO₂ 52.3 nm 72.9% 9.1% 14.6% SiO₂ 87.6 nmTiO₂ 52.3 nm SiO₂ 87.6 nm TiO₂ 52.3 nm

TABLE 6B Reflectance- Display Enhancement Transmit- Embodiment CoatingReflectance Transmittance tance (PT) 3200, 3202: 54.8% 36.9% 67.9% FIG.32 (A) TiO₂ 52.3 nm 3200, 3202: 68.7% 22.7% 40.0% FIG. 32 (A) TiO₂ 52.3nm SiO₂ 87.6 nm TiO₂ 52.3 nm 3200, 3202: 78.6% 12.7% 20.9% FIG. 32 (A)TiO₂ 52.3 nm SiO₂ 87.6 nm TiO₂ 52.3 nm SiO₂ 87.6 nm TiO₂ 52.3 nm 3210,3212: 54.6% 36.9% 67.9% FIG. 32 (B) TiO₂ 52.3 nm 3210, 3212: 68.2% 22.7%40.0% FIG. 32 (B) TiO₂ 52.3 nm SiO₂ 87.6 nm TiO₂ 52.3 nm 3210, 3212:77.7% 12.7% 20.9% FIG. 32 (B) TiO₂ 52.3 nm SiO₂ 87.6 nm TiO₂ 52.3 nmSiO₂ 87.6 nm TiO₂ 52.3 nm 3220, 3222: 59.4% 31.6% 57.5% FIG. 32 (C) TiO₂52.3 nm 3220, 3222: 72.3% 17.7% 30.5% FIG. 32 (C) TiO₂ 52.3 nm SiO₂ 87.6nm TiO₂ 52.3 nm 3220, 3222: 79.6% 9.7% 15.5% FIG. 32 (C) TiO₂ 52.3 nmSiO₂ 87.6 nm TiO₂ 52.3 nm SiO₂ 87.6 nm TiO₂ 52.3 nm

Generally, a means for opacification and a means for reflectanceenhancement may be combined or used alternatively in the areas of themirror assembly outside the display area (such as areas 644 of FIG. 6representing mirror areas outside of the display area 642) to reducevisibility of components located in those areas behind the mirror whilesimultaneously increasing the reflectivity. The value of transmittancein such outer areas 644 should be reduced, by either opacification, orenhancement of reflectance, or combination of both, to levels lower thanabout 10% and preferably lower than about 5%. In other embodiments, suchtransmittance may be reduced to levels lower than about 2.5% or evenlower than about 1%.

Various surfaces of the mirror assembly can be treated to simultaneouslyachieve the opacification and reflectance-enhancing effects, dependingon the requirements of a given application. For instance, in anembodiment comprising an EC element in front of the reflective polarizeras viewed by the observer (see, e.g., the embodiment 836 of FIG. 8(D)),a layer having both the opacifying and reflectance-enhancementproperties, further referred to herein as the opaquereflectance-enhancing layer (OREL), may be disposed on surfaces III, IV,V, or VI. In a related embodiment such as the embodiment 410 of FIG.4(C) or the embodiment 830 of FIG. 8(C) that comprised a reflectivepolarizer between the two lites of glass, one of which may be a prism,the OREL could be placed on surfaces I, II, III, or IV. Generally,positioning of the OREL behind the RP as viewed by the observe 115(e.g., close to surface V of FIG. 8(I)) boosts the reflectance of theRP-element and lowers the transmittance of the embodiment of the mirrorsystem beyond the mentioned increase of reflectance of the RP. Incomparison, in an embodiment where the OREL is disposed in front of theRP, as viewed by the observer, the OREL will provide a dominatingcontribution to the overall reflectance of the system, which can becalculated using standard thin-film modeling techniques. Transmittanceof an OREL is preferably sufficiently low to attain the transmittancetargets for the system defined above (i.e., concealing componentslocated behind the mirror assembly) while in some embodimentssimultaneously increasing the reflectance. Requirements imposed on anOREL differ from those for the reflectance-enhancing layers describedabove that are used for optimization of optical performance of thedisplay area of the mirror system. Materials for reflectance-enhancinglayer disposed in the display area of the mirror (transflective zone)are chosen so as to simultaneously optimize the reflectance andtransmittance of the transflective zone of the mirror, including thepolarized transmittance characteristic. (The efficiency of suchperformance enhancement was described using the PT/R ratio, in Table 3,for example). In the areas outside of the display area (opaque areas),however, there is no need to preserve the value of polarizedtransmittance and other materials such as metals, borides, nitrides,carbides, and sulfides may be used to enhance the reflectance of and toopacify these areas.

Both the overall (unpolarized light) reflectance of the mirror assemblyand the reflectance of light having a particular polarization depend ona material structure of the assembly. A description of a materialstructure of a mirror assembly can be provided, e.g., by listingmaterial components of such a structure in the order starting from acomponent that is distal to the viewer towards a component that isproximal to the viewer. A structure of the embodiment 830 of FIG. 8(C)can be described as [G/RP/G](where G, RP, and G respectivelycorresponding to components 826, 824, and 832), while a structure of theembodiment 836 of FIG. 8(D) can be similarly described as[G/RP/G/ITO/EC/ITO/G](where the listed components respectivelycorrespond to components 826, 824, 610, 808, 614, 817, and 635).

FIG. 11 illustrates the depolarizing effect of an OREL on performance ofthose areas of the mirror structure that are located outside of thedisplay area. FIG. 11 schematically shows a section 1100, of anembodiment of the mirror system, corresponding to one of the areas 644of FIG. 6. The section 1100 includes a front portion 1110, defined as aportion of the mirror system located between the viewer 115 and anelement disposed behind the RP 824, and an OREL 1120 that is opticallyconnected to the front portion 1110 through an optional adjacent medium1130. In practice, the adjacent medium 1130 when present may includeair, polymer, adhesive, or other medium. The OREL may be directlydeposited onto the RP or, alternatively, it may be deposited on anadditional lite of glass that is further bonded to the RP. By way ofexample, a front portion of the embodiment of FIG. 8(D) would includethe EC element 840 and the reflective polarizer 824 portion of thelaminate 828. A corresponding front portion of the embodiment of FIG.8(E) would contain the EC element 840, the bi-layer 846, and thereflective polarizer 824. Referring again to FIG. 11, a portion 1140 ofincident ambient light 1150 having a first polarization that ispredominantly transmitted by the RP 824 will pass through the frontportion 1110 of the mirror system and the optional adjacent medium 1130and will be reflected by the OREL 1120 back towards the viewer 115, asindicated by an arrow 1155. A complementary portion 1160 of ambientlight 1150, having a second polarization that is opposite the firstpolarization, is substantially reflected by the RP 824 towards theviewer 115 and combines with the beam 1155. When the two reflected beams1155 and 1160 having opposite polarizations are combined, a degree ofpolarization of the overall reflected beam 1170 is not as high as itcould be otherwise. The use of an OREL in some embodiments of thepresent invention, therefore, allows for a less-polarized reflection oflight from the mirror assembly towards the viewer and simultaneousincrease in the overall reflectance of the assembly. The use of ORELserves to effectively depolarize the light. A degree of lightdepolarization can be varied by appropriately selecting materials forOREL and adjacent media separating the OREL and RP.

Referring again to FIG. 11, multiple reflections within the mirrorassembly may be taken into account. The amount of net reflectance 1180can be calculated, as is well known in the art, based on the indexdifferences at the interfaces within the mirror assembly, the values ofabsorbance and thicknesses of the materials involved, and the value oftransmittance of the reflective polarizer averaged over twopolarizations (the preferred polarization of light generated by thedisplay and the one orthogonal to it). By way of example, in aparticular embodiment the front portion of the mirror assembly,including the reflective polarizer, reflects unpolarized light with44.5% efficiency, transmits light of preferred polarization withefficiency of 81.8%, and transmits only 3.0% of light having orthogonalpolarization. An OREL with a reflectance of 70% in air as adjacentmedium, as shown in FIG. 13, will result in the net added reflectance of[0.818*0.7*0.818+0.03*0.70*0.03]*0.5=0.2345, or 23.45% In such a case,the overall reflectance of the embodiment of FIG. 11 would be the sum of44.5% and 23.45%, or about 68%. Reflectance properties of the ORELdepend, in part, on the refractive index of the adjacent medium 1130.For instance, the reflectance of a metal surface in contact withdielectric material is reduced as the refractive index of suchdielectric material is increased. Reflectance of OREL including achromium/ruthenium bi-layer (500 Å of chromium and 200 Å of ruthenium)in air as the adjacent medium 1130, e.g., may be about 70%. However, thereflectance of the same bi-layer OREL with a dielectric adjacent mediumhaving an index of 1.51 will reach only about 58.5%.

(E.4) Additional Embodiments

Table 7 shows experimentally determined reflectance andcolor-qualification parameters associated with various embodiments ofthe invention. In the following, Samples 1 through 7 are located in air(i.e., air is the incident medium). Sample 1, representing a simplemirror formed by an approximately 500 Å thick single layer of chromiumon a glass substrate, has a reflectance of 57%. Sample 2 represents alaminate including a reflective polarizer (DBEF-Q film) laminated tosurface IV of an EC-element (with ITO coatings on surfaces II and III)according to the method of the invention, and corresponds to theembodiment 836 of FIG. 8(D) with the lite 826 removed. Sample 2 reflectsabout 44.4% of the unpolarized light. Sample 3 represents a combinationof the sample 1 disposed behind the sample 2 and separated from it by anair gap. The overall reflectance of Sample 3 is about 66%. Sample 4represents the embodiment 836 of FIG. 8(D). As can be seen from thecomparison of optical characteristics of Samples 3 and 4, the additionof the third lite of glass 826 does not appreciably affect thereflectance of the mirror assembly. Sample 5 is constructed bypositioning Sample 1 behind Sample 4 and separating them with anair-gap. Sample 5 has a reflectance value comparable to that of Sample3. Sample 6 represents a bi-layer coating (including an approximately500 Å thick chromium layer and an approximately 200 Å thick rutheniumlayer deposited on glass in that order. The reflectance of sample 6 ismeasured in air (air is the adjacent incident medium) and equals about69.8%. Sample 7 describes the embodiment where sample 6 is behind sample2 with an air gap. The reflectance is increased from about 44% to morethan 71%. As noted above, the refractive index of the incident mediumadjacent a metallic layer affects the reflectance of the metallic layer.The index-matching oil, used instead of air as incident medium withSamples 8 and 9, has a refractive index of approximately 1.5, and isused to suitably simulate laminations with materials such glass orplastics with similar refractive indices. In these examples, the use ofthe index-matching oil is optically comparable to having the coatedglass laminated to the mirror assembly on the rearward surface. Asdescribed above, the reflectance of a metal coating is decreased whenthe index of the adjacent medium is higher than 1. The index-matchingoil or laminate has a refractive index of about 1.5 and thus lowers thereflectance values of Samples 8 and 9 in comparison with Sample 7.

Sample 6, discussed in reference to Table 7 and having achromium/ruthenium bi-layer, demonstrates spectrally neutral reflectance(with a* and b* values near zero). Other metals or compoundscontemplated in this embodiment may be used to provide opacification,reflectance enhancement and/or color tuning. Different metals andcompounds may have different reflected colors and can therefore be usedto tune the color of the coating stack in the region outside the displayarea as taught, for example, in U.S. patent application Ser. No.11/833,701 (now published as U.S. 2008/0310005) and Ser. No. 12/370,909(now published as U.S. 2009/0207513), each of which is incorporatedherein in its entirety by reference.

TABLE 7 Sample # Description of Embodiment R a* b* 1 Mirror with R = 57%57.0 −1.1 1.5 2 An EC-element with ITO 44.4 −2.1 2.4 coatings onsurfaces II and III and APBF laminated to surface IV 3 Sample 1positioned behind 65.8 −3.7 1.90 sample 2, with air gap in between 4 AnAPBF laminated between 44.7 −2.0 −2.5 the EC-element (comprising ITOcoatings on surfaces II and III) and third lite of glass (see embodiment836 of FIG. 8 (D) 5 Sample 1 positioned behind 65.9 −3.0 1.9 sample 4,with air gap in between 6 Chromium/Ruthenium bi-layer 69.8 0.0 0.1 onglass substrate 7 Sample 6 positioned behind the 71.4 −3.5 1.6 APBF ofsample 2, with bi- layer facing APBF and separated from APBF by air- gap8 Sample 6 adjacent to sample 4 66.8 −3.5 1.6 with index-matching oilbetween bi-layer and APBF 9 Sample 6 adjacent to sample 2 66.5 −3.4 1.6with index-matching oil between bi-layer and APBF

By analogy with graded opacifying layers discussed in reference to FIG.17, an OREL layer (assuring both the opacification andreflectance-enhancement effects, as discussed above) may also exhibit agraded transition between the display area and the adjacent opaque area.In one embodiment, the OREL is located behind the APBF, is absent (haszero effective thickness) in the area of the display and graduallyincreases its thickness (and, therefore, reflectivity) across thesurface towards the “opaque” region. Optionally, a thin transflectivelayer (e.g., an OREL layer or another transflective layer) with finitethickness may be present at the display area to facilitate adhesionand/or optimize aesthetic appearance of the rearview mirror. The gradualtransition of the OREL layer would achieve the effect of concealing atleast one edge of the display area. In addition, the gradual transitionadditionally provides a benefit of grading the reflectance between thetwo regions in a manner taught in a commonly assigned U.S. patentapplication Ser. No. 11/833,701, incorporated herein by reference in itsentirety. The gradual transition in reflectance or transmittance is notreadily noticed by an observer and a relatively large difference ofreflectance or transmittance between a display and another region canexist without being readily apparent to a casual observer. In contrast,if a discrete transition is present, the interface between the regionsbecomes noticeable even with very small changes in reflectance ortransmittance. Similarly, if the color changes gradually, the differencebetween two regions is harder to perceive. By way of example, in theembodiment 889 of FIG. 8(J), a graded chromium OREL coating 886 may bedeposited on a glass substrate 890 and positioned behind the surface VIof the embodiment 836 of FIG. 8(D). A gap 892 between the surface VI andthe Cr-layer is filled with the index-matching oil having a refractiveindex of 1.5. As shown, the chromium coating is absent on the portion ofthe glass 890 that overlaps with the display region of the assembly andtransitions from zero thickness to approximately 500 Å (in the opaqueregion) over the extent of about 1.5″. FIG. 12 shows a gradual, withoutdiscontinuities change in reflectance of the embodiment 889 of FIG. 8(J)as a function of position, measured from the display region through thetransition region to the region of full opacity in 0.25 inch increments.Table 8 shows the corresponding reflectance values (cap Y) and thereflected color (a* and b*). As can be seen from Table 8, the colorvariation is also smooth and the color difference between the two zones(the display region and the opaque region) is minimal. Preferably, thecolor difference between the two regions (the display region and theregion of full opacity) is less than 5, preferably less than 3, mostpreferably less than 1 units. The color difference ΔC* is defined usingthe following formula:

Color Difference=ΔC*=√{square root over ((a*−a*′)²+(b*−b*′)²)}

where (a*, b*) and (a*′,b*′) are the values describing color of lightreflected by the mirror system at two different positions across themirror.

TABLE 8 Position (inches) Cap Y a* b* 0 46.4 −2.0 −2.3 Display 0.25 46.3−2.1 −2.2 Area 0.5 46.2 −2.0 −2.3 0.75 46.1 −2.0 −2.4 1 46.2 −2.0 −2.31.25 46.7 −2.1 −2.2 Opaque 1.5 48.7 −2.4 −1.6 Area 1.75 52.2 −3.0 −0.7 256.1 −3.4 0.1 2.25 60.4 −3.7 0.8 2.5 65.0 −3.8 1.4 2.75 66.3 −3.8 1.5

In another example of a sample made in accordance with embodiment 884 ofFIG. 8(I), a graded chrome layer is deposited on top of a TiO₂/ITOreflectance-enhancing layer 846 on surface V of a 1.1 mm thick lite ofglass 826. The TiO₂ portion of the coating is about 45 nm and the ITOportion is about 18 nm thick. The EC-element 840 is constructed of 2lites of 1.6 mm-thick clear glass (610 and 635) with a EC-cell gap of150 microns. The thickness of the ITO coatings on surfaces II and IIIare approximately 150 nm thick each. Optical characteristics of thissample as measured in reflection and transmission are summarized inTable 8A. The ratio of polarized transmittance to overall reflectance isapproximately 1.4 for this configuration.

TABLE 8A Reading in Reflection Transmittance, T, % Reflectance, R, % a*b* p-polarization s-polarization PT/R Display Area (transflective area)51.7 −2.0 −2.0 5.2 73.2 1.42 Area Outside the Display Area (opaque area)66.3 −3.2 0.0 0.0 0.4

The graded zone may generally consist of a single graded metal, alloy orcompound, or it may consist of multiple layers selected and designed toattain desired reflectance and transmittance in the opaque region, thedesired reflected color in the opaque region, and the transitionbehavior between the display and opaque regions. The transition regionmay be characterized by the rate of change of reflectance or color, orthe layers may be designed to minimize the color difference between thetwo zones with no undesired color behavior in the transition zone.

Exemplary Embodiments for Use in Conjunction with an External PolarizingElement.

In some embodiments, light generated by the display of the embodimentsis polarized, for example, when a LCD is used with a mirror assembly. Inreference to the embodiments of FIG. 8(A) or 8(D), for example, theportion of the display-generated light 820 that traverses the componentsof the mirror assembly and reaches the viewer 115 is typically linearlypolarized at about 45 degrees to the vertical, which is represented inFIGS. 8(A,D) by y-axis. Such orientation of the LCD-generated light isdictated by a conventional structure of an LCD, which comprises acorrespondingly oriented linear polarizer through which the light passesupon being emitted. For normal indoor viewing of LCD displays, the angleof polarization of the emitted light does not directly affect theviewer's ability to see the displayed image. However, when an LCDdisplay is to be viewed outdoors or in a vehicle, where the ambientlight is sufficiently bright, the user may be wearing sunglasses. Theuse of sunglasses and, in particular, polarizing sunglasses, by thedriver of an automotive vehicle may become a criterion for design ofautomotive mirror assemblies that comprise displays.

Typically, polarizing sunglasses employ a linear polarizer to reduce theintensity of an apparent glare originating from reflection of ambientlight from various surfaces. The reflection of light is described bywell-known Fresnel equations that take into account a polarization stateof light. For example, polarizing sunglasses that utilize a polarizingfilter with a transmission axis oriented vertically (i.e., alongthey-axis as seen in FIG. 8(A), for example) reduce the intensity of thes-polarized (horizontal) component of ambient light thereby reducing theapparent glare from horizontal surfaces. Since the vector of linearpolarization angle of light emitted by most LCD displays isconventionally oriented at 45 degrees relative to the transmission axisof the typical polarizing sunglasses, the brightness of the LCD displayperceived by the user wearing such polarized sunglasses will be reducedby about 50%. For a driver of an automotive vehicle that observes thedisplay in the rearview mirror assembly the perceived reduction of thedisplay intensity may be undesirable.

In one embodiment, the light output of the display may be depolarized bya depolarizer such as a stretched polyester film, for example, or anyother suitable depolarizer. The use of a depolarizer is describedgenerally above and in detail in a commonly assigned U.S. PatentPublication 2008/0068520. As shown in FIG. 13(A), a depolarizer 1302 maybe placed between the display 639 and the transflective mirror assembly1304 (which may be, for example, the embodiment 800 of FIG. 8(A) or anyembodiment of the mirror system of the present invention).Depolarization of light 820 from the display prevents the polarizingsunglasses 1306 from interfering with the driver's ability to perceivethe display light. A similar depolarizing effect may be obtained, forexample, in an mirror structure embodiment 2020 of FIG. 20, by placing adepolarizer 2010 between the reflecting polarizer 824 (DBEF-Q) and theglass substrate 610 of the electrochromic element 840. As shown, theembodiment 2010 of FIG. 20 is similar to the embodiment 836 of FIG. 8(D)but it contains, in addition, the depolarizing layer 2010 comprisingstretched polyester such as Flexmark PM™ 200 or uncoated PP2500transparency film (available from 3M, Inc.) placed between thereflective polarizer 824 and the observer 115. As shown, a layer 2030 ofpressure sensitive adhesive (PSA) may be operationally connecting the RP824 and the depolarizer 2010. In another embodiment, the same effect maybe obtained by placing a depolarizer directly on the face of a mirrorassembly. In an embodiment similar to any of the embodiments of thecurrent invention, such as the embodiment of FIG. 8(D), for example, adepolarizer may be disposed on surface I of the glass plate 635. Inanother embodiment, the same effect may be obtained by using adepolarizing transparent layer such as plastic layer, in place one orboth of the lites of glass forming an EC-cell. For example, in oneembodiment, at least one of the plates 610 and 635 of FIG. 8(D) may bemade of a depolarizing plastic material. In another embodiment, the sameeffect may be obtained through the use of an optically anisotropic orbirefringent material placed in the electrochromic fluid of theEC-element (such as the element 614 in FIG. 8(D)). The degree ofpolarization can be defined as extinction value,(T_(high)−T_(low))/(T_(high)+T_(low)), where high and low represent theintensity values of light in the two polarization states having,respectively, high and low intensity. When light is highly polarized,the extinction value will be high. Table 9 below shows the transmittedand reflected polarization values for systems with and without opaquemetals present. Both transmission and reflection cases represent arelatively high extinction baseline for the system without the additionof a depolarizer. The samples used are described in Table 9 and twoexperimental samples of each configuration are shown. The high and lowpolarized intensity values are also listed. These values are used tocalculate an extinction percentage using the formula defined above. Lowextinction values equate to relatively equal intensities of the twopolarization states. The difference value listed in Table 9 representsthe percent

TABLE 9 Sample Description low high Extinction Difference TransmittanceUncoated 1.6 mm glass/8161 PSA/depolarizer/DBEF/¼ 18.4 60.5 53.36%35.97% wave TiO2-ITO bi-layer coating on 1.6 mm glass Uncoated 1.6 mmglass/8161 PSA/depolarizer/DBEF/¼ 20.3 58.8 48.67% 40.66% wave TiO2-ITObi-layer coating on 1.6 mm glass Uncoated 1.6 mm glass/depolarizer/3MPSA DBEF/¼ wave 22.5 58.8 44.65% 44.68% TiO2-ITO bi-layer coating on 1.6mm glass Uncoated 1.6 mm glass/depolarizer/3M PSA DBEF/¼ wave 23 54.440.57% 48.76% TiO2-ITO bi-layer coating on 1.6 mm glass Uncoated 1.6 mmglass/depolarizer/DBEF/¼ wave TiO2- 21.1 53.9 43.73% 45.60% ITO bi-layercoating on 1.6 mm glass Uncoated 1.6 mm glass/depolarizer/DBEF/¼ waveTiO2- 24.3 53.2 37.29% 52.04% ITO bi-layer coating on 1.6 mm glassUncoated 1.6 mm glass/DBEF/uncoated 1.6 mm glass 5.1 90.5 89.33% 0.00%Reflectance Uncoated 1.6 mm glass/8161 PSA/depolarizer/DBEF/chrome 59.484.3 17.33% 9.48% coating on 1.6 mm glass Uncoated 1.6 mm glass/8161PSA/depolarizer/DBEF/chrome 60.1 83.9 16.53% 10.28% coating on 1.6 mmglass Uncoated 1.6 mm glass/depolarizer/3M PSA DBEF/chrome 65.5 76.57.75% 19.06% coating on 1.6 mm glass Uncoated 1.6 mmglass/depolarizer/3M PSA DBEF/chrome 63 80 11.89% 14.92% coating on 1.6mm glass Uncoated 1.6 mm glass/depolarizer/DBEF/chrome coating 61.5 81.914.23% 12.58% on 1.6 mm glass Uncoated 1.6 mmglass/depolarizer/DBEF/chrome coating 65.1 80.3 10.45% 16.36% on 1.6 mmglass Uncoated 1.6 mm glass/DBEF/uncoated 1.6 mm glass 53.1 92 26.81%0.00%

The samples described in a “Reflectance” portion of Table 9 (the“reflectance samples”) show about a 40% to 50% improvement in theextinction. Visual examination of these samples with Polaroid sunglassesshowed a substantially decreased sensitivity to head tilt and,therefore, less changes due to head tilt in the reflected andtransmitted light. The term head tilt refers to rotation of thepolarization system of the polarizing sunglasses. The mirror systemcontaining such samples has lower initial extinction values than thesystem containing samples described in “Transmittance” portion of Table9 (the “transmittance samples”). This is due to the presence of a metallayer behind the reflective polarizer reflecting a substantialpercentage of the “low” polarization state. The presence of chrome layerin “reflectance samples” adds approximately 40% more light of the lowpolarization state relative to the high state. This gives the initialreference system without the depolarizer an extinction value of about26%, essentially comparable with or better than that of the system thatincludes a “transmission sample” and a depolarizer. The extinction valuecan be further reduced by substituting the chrome with a metal havinghigher reflectance. This, as noted above, will increase the reflectanceof the system and simultaneously reduce the extinction value by addingmore light in the “low” polarization state. This beneficialcharacteristic enables another possible embodiment—the benefits of adepolarizer can be obtained without a depolarizer in the area where thechrome, metal or other reflectance enhancement means is present and theadjustment of the LCD/reflective polarizer's polarization angle can bejudicially performed to more closely match the transmitted state of thePolaroid sunglasses (as discussed above). The reflected image in thearea of the display would be reduced in a commensurate amount whenviewed with Polaroid sunglasses but the image in the remainder of themirror would remain relatively high. A viewer not using Polaroidsunglasses would not be affected by this particular configuration.

In a related embodiment, the brightness of the display, perceived by thedriver wearing polarizing sunglasses, may be increased by rotating thevector of polarization of the display-generated light, upon light'spassing through the mirror assembly towards the driver, to make itco-linear with the transmission axis of the sunglasses. As shown in FIG.13(B), for example, such rotation may be achieved with the use of apolarization rotator 1308 appropriately disposed in front of thetransflective mirror assembly 1304 to reorient the polarization vectorof light 820′, emanating from the assembly 1304 towards the user 115,along the transmission axis of the sunglasses 1306. In a specificembodiment, the polarization rotator 1308 may comprise a half-wave plate(made of a birefringent film, for example) having its transmission axisalong the bi-sector of an angle formed by the transmission axis of thepolarizing sunglasses and the polarization vector of light 820′. As aresult, the polarization vector of light 820, initially oriented inxy-plane at 45 degrees with respect to the y-axis, will be aligned withthe x-axis, according to the well-known principle of operation of thehalf-waveplate.

In an alternative embodiment (not shown), it may be preferred to disposethe LCD as a whole (or, alternatively, only the polarizing components ofthe LCD) at a predetermined angle in an xy-plane within the rearviewmirror so as to produce light emission 820 that is initially polarizedalong the transmission axis of the sunglasses worn by the driver. Insuch alternative embodiments, light 820 emitted by the LCD 639 may bep-polarized (i.e., polarized along the x-axis). If, in addition, thereflecting polarizer (which may be a part of transflective mirrorassembly 1304 according to any of embodiments of the present invention)is oriented so as to maximize the transmission of the LCD light 820through the transflective assembly, the brightness of the LCD perceivedby the driver 115 through the sunglasses 1306 may be also optimized. Forexample, in reference to FIG. 13(A), a conventionally oriented LCD 639may emit light with luminance of 1,000 cd/m² and lenses of thepolarizing sunglasses 1306 may transmit 20% of p-polarized light and 0%of s-polarized light. Then, the transmission of unpolarized lightthrough polarizing sunglasses 1306 will be about 10%. Should adepolarizer 1302 be used between the LCD 639 and the transflectiveassembly 1504, the effective luminance of LCD light reaching the user115 through the sunglasses 1306 would be about 100 cd/m². In comparison,if the LCD system is oriented to provide p-polarized light output 820,the effective luminance perceived by the observer 115 through the samepolarizing lens 1306 increases to about 200 cd/m². At the same time, thebrightness of the ambient light reflected by such embodiment towards thedriver in sunglasses may be minimized, which worsens the performance ofthe mirror assembly as a reflector. The use of depolarizer 1302 with aconventionally oriented LCD 639, as shown in FIG. 13(A), may thereforebe preferred overall to rotating the LCD as described above.

In the following, additional embodiments of the invention are discussedand compared in reference to FIG. 3. In one embodiment, the composite312 was vacuum bagged, then placed into an autoclave for 1 hour at 90°C. at 100 psi. The resulting laminate 314 did not display any pattern ofdegradation and showed substantially no obvious extended distortions.FIG. 14 shows an image of a reference grid formed in reflection,according to the visual evaluation test, from another embodiment of thelaminate comprising a 1.6. mm thick glass substrate and a DBEF-Q film.The superstrate, preliminarily treated with Aquapel®, was released fromthe laminate according to the embodiment of the invention. This laminatewas prepared by vacuum bagging and autoclaving at about 90° C. and 200psi for about an hour and demonstrates quality adequate for automotiveuse. Generally, the temperature chosen for lamination processes in theabove implementations approximately corresponds well to the start of theglass transition onset temperature of the DBEF-Q polarizing film, asshown in FIG. 15. The glass transition temperature of the plastics is awell known physical characteristic of a plastic or multilayer plasticstructure and based on these experiments the lamination temperatureshould preferably be at or near the T_(g) in order to attain a laminatewith optical properties sufficient for automotive use. There exists aninterrelationship between the pressure, temperature, humidity, and timenecessary for a given APBF material to attain the desired opticalproperties. For instance, it may be possible to shorten the laminationtime if higher lamination pressure is applied at a slightly higherlamination temperature. We also discovered that the temperature forlamination of the reflective polarizer material may be controlledsomewhat independently from that of the substrate by using infraredheating at wavelengths that are transparent for the glass but absorbingby the reflective polarizer. In this manner the stress profiles in thematerials used for lamination may be controlled or modified, thereforefacilitating higher quality of the resulting laminate.

In contradistinction, and as a comparative example of a commercialproduct produced with a reflective polarizer having unacceptablereflective optical properties, a laminate-containing reflector (formedby a display of “Miravision” mirror-television set, manufactured andsold by Philips Corporation, model number 17MW9010/37, S/N1BZ1A0433816730, manufacture date August 2004) was also evaluated fordistortions. The inside frame dimensions of the sample are indicated ina diagram of FIG. 16. This commercial product included an opaquereflective area 1602 in the upper portion of the sample and a partiallyreflective/partially transmissive area 1604 in front of a display in thelower portion of the display, as indicated in the diagram. The mirror inthe lower portion obtains at least part of its reflectance by the use ofa reflective polarizer. The sample was examined using the visualevaluation test described above. The sample showed extended distortionsin the display region, particularly in they-direction. Furthermore, asperceived visually, the waviness of the reflective laminate wasexacerbated if the viewer moved his head relative to the mirror. Thisworsening of the optical distortion with relative motion is aparticularly negative trait for automotive mirror applications, where areflected image must be equally well perceived at various angles. Thissample proved to be unacceptable for use in an automotive rearviewmirror, similarly to the commercial reflector described with referenceto FIG. 2. Specific results of evaluation of this sample withBYK-Gardner wave-scan dual device are provided in Table 10. As shown,the average of three short-wave and long-wave (SW and LW, respectively)readings were taken directionally in x- and y-direction, in thecorresponding regions labeled as X1 . . . X3 and Y1 . . . Y3 in FIG. 16.The values of SW in excess of 3, measured in the y-direction, areconsistent with the presence of the unacceptable waviness. Thisconclusion is also supported by the fact that several of the Wa, Wb andWe metrics are greater than 7. Characterization of the region of theopaque mirror outside the display area demonstrates values that aresubstantially lower than those taken in the display region.

TABLE 10 LW SW Wa Wb Wc X1 (avg) 0.5 0.5 6.8 6.2 1.2 X2 (avg) 1.1 0.56.4 6.2 2.4 X3 (avg) 0.7 0.5 6.7 6.3 1.6 Y1 (avg) 0.2 3.6 7.7 9.2 2.5 Y2(avg) 0.3 3.9 7.7 9.0 0.7 Y3 (avg) 0.2 3.5 7.9 9.0 0.7 XM (avg)  0 0 1.61.2 0.0 YM (avg)  0 0 1.7 1.4 0.1

Durability Testing. (1) High Temperature, High Humidity, and ThermalShock Testing.

In certain applications the laminate containing a reflective polarizeris exposed to relatively harsh environments. Automotive applications arean example of an environment that requires a component to pass stringentdurability tests (environmental durability tests) for the product to bequalified for use. The durability tests vary by automotive company butthere are a number of common tests a product is expected to pass. Thetests are designed to ensure that a product will function adequately forthe life of a vehicle. One of the tests is a so-called “hightemperature/high humidity” test, where the part or component is placedin a test chamber, e.g., at approximately 85° C. and 85% humidity. (Theprecise temperature, humidity and duration of the test can varydepending on the requirements of an automotive company.) Another test isa “high temperature storage” test where the component is kept at about105° C. for various lengths of time. (Four days or 96 hours is a commonduration of such test.) In other tests the component is kept at lowertemperature (85° C.) for up to 1,500 hours. Yet another test is a socalled “thermal shock” test, where the component repeatedly undergoesheating and cooling in cycles, e.g., between −40° C. and +85° C., with 1hour dwell, often with high humidity conditions. The hold time, ramptime, temperature extremes and number of cycles may vary depending onthe requirements imposed by an automotive company. Other tests have beendeveloped which combine the extreme conditions of the tests listed aboveto examine interaction effects. A failure in one or more of these testsmay be sufficient to prevent a given embodiment of a fabricatedcomponent or product from being commercialized. As a result ofenvironmental testing of various laminate embodiments of the inventionit was discovered that, generally: (i) embodiments fabricated at lowerlevels of pressure, such as 50 psi, have decreased durability; (ii) withincrease in lamination time, the durability of embodiments tends toincrease; (iii) an embodiment of the laminate of the invention havingboth a substrate and a superstrate (such as embodiment 314 of FIG. 3(C))has higher durability than the one with a superstrate released, whichdurability may be improved by post-lamination annealing.

Specifically, comparison of environmental durability of laminates havinga superstrate and those with a superstrate release was determined byfabricating and testing the samples made by laminating an APBF filmbetween the EC-element and the third lite of glass, according to thestructure of the embodiment 850 of FIG. 8(F) that additionally had agraded-thickness chromium layer deposited adjacent surface V. Prior tofabrication, the moisture content of the APBF film was maintained withinthe preferred limits as discussed above. The third lite of glass 826 waspre-treated with a release agent, as discussed in reference to FIG. 3,to allow for optional release of the superstrate 826. The laminatesamples under test were assembled along with control samples,vacuum-bagged, and autoclaved at 95° C. and 200 psi (gauge pressure) forabout 1 hour. All laminates were initially inspected visually fordefects and then exposed to the following environmental durabilitytests: 1) High Temperature Storage (105° C.), 2) High Temperature/HighHumidity Storage (85° C./85% RH), and 3) Thermal Shock (−40 to 85° C., 1hr dwell). The samples were inspected visually at variable timeintervals for various defects that are specific to individualenvironmental durability tests. Results of these tests are shown inTables 11, 12, and 13, respectively. As follows from these Tables, thelaminate embodiments that have a superstrate released (unprotectedsamples), even if initially acceptable through visual inspection, becameunacceptable for intended as a result of environmental durabilitytesting.

TABLE 11 High Temperature Storage test, 105° C. Sample Description 0 hrs24 hrs 48 hrs 72 hrs 96 hrs 168 hrs 336 hrs 504 hrs 672 hrs Control #1xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxx Control #2 xxxxxxxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxx Unprotected #1 xxxxxxxxxx xxx xxx xxx xxx xxx xx xx Unprotected #2 xxxxx xxxxx xxxx xxx xxxxxx xxx xx xx Legend: xxxxx = Excellent, no defects xxxx = Acceptable,small defects xxx = Unacceptable, bubbling, delamination, haze xx =Unacceptable, significant bubbling, delamination, haze x = Unacceptable,severe bubbling, delamination, haze Blank = Removed from testing

TABLE 12 High Temperature/High Humidity Storage test, - 85° C./85% RHSample Description 0 hrs 24 hrs 144 hrs 312 hrs 480 hrs 624 hrs 766 hrsControl #1 xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx Control #2 xxxxxxxxxx xxxxx xxxxx xxxxx xxxxx xxxxx Unprotected #1 xxxxx xx xx xx xx xxxx Legend: xxxxx = Excellent, no defects xxxx = Acceptable, smalldefects xxx = Unacceptable, bubbling, delamination, edge ingress xx =Unacceptable, significant bubbling, delamination, edge ingress x =Unacceptable, severe bubbling, delamination, edge ingress Blank =Removed from testing

TABLE 13 Thermal Shock test, −40 to 85° C., 1 hr dwell Sample 75 150 213433 493 568 Description 0 hrs cycles cycles cycles cycles cycles cyclesControl #1 xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx Unprotected #1xxxxx xx x X X x x Legend: xxxxx = Excellent, no defects xxxx =Acceptable, small defects xxx = Unacceptable, bubbling, delamination,edge ingress xx = Unacceptable, significant bubbling, delamination, edgeingress x = Unacceptable, severe bubbling, delamination, edge ingressBlank = Removed from testing

A similar set of experiments was directed to more completely understandthe effect of a post-lamination superstrate release on the durability ofa laminate of the invention. In this case, an APBF film was laminated,according to the embodiment 850 of FIG. 8(F), where glass lites 610 and826 were not coated with additional thin-film layers. Surface V of lite826 was pre-treated with a release agent to facilitate thepost-lamination release of the lite 826. This was accomplished byincorporating a release agent which allows for the removal of one liteof glass after lamination. Fabrication of both the samples under testand control samples was carried out under the conditions described inreference to Tables 11, 12, and 13. However, to improve adhesion of theAPBF to the uncoated glass plate 610, the samples were additionallyannealed post-lamination for 0, 30, or 60 minutes at 105°. The laminatedparts were initially inspected visually for defects and then submittedfor environmental durability testing: 1) High Temperature Storage (105°C.), 2) High Temperature/High Humidity Storage (85° C./85% RH), and 3)Thermal Shock (−40 to 85° C., 1 hr dwell). The parts were inspectedvisually at variable time intervals for various defects which arespecific to the individual environmental durability test. Results of theabove-mentioned tests, shown in Tables 14, 15, and 16, respectively,demonstrate that embodiments of the laminates the parts unprotected by ssuperstrate (i.e., having a superstrate 826 released) demonstrate poordurability in comparison with control samples. The unprotected sampleswere initially marginally acceptable or unacceptable by visualinspection but quickly all became unacceptable for use when subjected toenvironmental durability testing. The extra lite of glass incorporatedinto this embodiment significantly increases the environmentaldurability of the laminated devices.

TABLE 14 High Temperature Storage test, 105° C. Sample Description 0 hrs120 hrs 168 hrs 288 hrs 456 hrs 624 hrs 792 hrs 960 hrs Control xxxxxxxxxx xxxxx xxxxx xxxx xxxx xxxx Xxxx Control xxxxx xxxxx xxxxx xxxxxxxxxx xxxxx xxxx Xxxx 30 Minute Control xxxxx xxxxx xxxxx xxxxx xxxxxxxxxx xxxxx Xxxx 60 Minute Superstrate (3^(rd) lite) xx xx Xx xx x x x XRemoved, Control Superstrate (3^(rd) lite) xx xx Xx xx x x x x Removed,30 Minutes Superstrate (3^(rd) lite) xxxx xxx Xxx xxx xx xx xx xxRemoved, 60 Minutes Legend: xxxxx = Excellent, no defects xxxx =Acceptable, small defects xxx = Unacceptable, bubbling, delamination,haze xx = Unacceptable, significant bubbling, delamination, haze x =Unacceptable, severe bubbling, delamination, haze Blank = Removed fromtesting

TABLE 15 High Temperature/High Humidity Storage test, 85° C./85% RHSample Description 0 hrs 96 hrs 264 hrs 408 hrs 552 hrs 696 hrs 792 hrs960 hrs Control xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx Controlxxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx 30 Minutes Control xxxxxxxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx 60 Minutes Superstrate (3^(rd)lite) xx x Removed, Control Superstrate (3^(rd) lite) xx xx x Removed,30 Minutes Superstrate (3^(rd) lite) xxxx xx x Removed, 60 MinutesLegend: xxxxx = Excellent, no defects xxxx = Acceptable, small defectsxxx = Unacceptable, bubbling, delamination, edge ingress xx =Unacceptable, significant bubbling, delamination, edge ingress x =Unacceptable, severe bubbling, delamination, edge ingress Blank =Removed from testing

TABLE 16 Thermal Shock - −40 to 85° C., 1 hr dwell Sample 135 205 280355 430 610 Description 0 hrs cycles cycles cycles cycles cycles cyclesControl xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx xxxxx Control xxxxx xxxxxxxxxx xxxxx xxxxx xxxxx xxxxx 30 Minutes Control xxxxx xxxxx xxxxx xxxxxxxxxx xxxxx xxxxx 60 Minutes Superstrate (3^(rd) lite) xx x Removed,Control Superstrate (3^(rd) lite) xxxx x Removed, 30 Minutes Superstrate(3^(rd) lite) xx x Removed, 60 Minutes Legend: xxxxx = Excellent, nodefects xxxx = Acceptable, small defects xxx = Unacceptable, bubbling,delamination, edge ingress xx = Unacceptable, significant bubbling,delamination, edge ingress x = Unacceptable, severe bubbling,delamination, edge ingress Blank = Removed from testing

The following series of samples were laminated via vacuum bagging andautoclaving (the latter occurring in pressurized gas or liquid) at 200psi and approximately 90° C. The different embodiments are contrastedusing thermal storage at 105° C. and 48 hours. These particular testconditions are not meant to be limiting and subtle differences betweenthe tests and laminates may be found with other tests or durations:

A laminate structured as [G/PSA/DBEF-Q/G], with PSA thickness of about 1mil, resulted in good image-forming quality and retained good qualityfollowing 48 hours of 105° C. storage.

A laminate structured as [G/DBEF-Q/G], where one of the glass plates hadbeen pretreated with a release agent (Aquapel™ available from PPGIndustries, Inc.) and then removed after the lamination procedureaccording to an embodiment of the invention, had good initial mirrorquality and retained good optical properties, i.e., image preservingreflector, following 48 hours of 105° C. storage.

The long-term stability of laminate-containing embodiments was monitoredby measuring the haze within the display region of the mirror structure.According to the standards of ASTM (American Society for Testing andMaterials), haze is defined as percentage of light that, duringtransmission through a sample, deviates by more than 2.5 degrees fromthe direction of the incoming beam of light. Haze measurements oflaminates structured according to the embodiment 850 of FIG. 8(F) wereaccomplished using a BYK Haze-gard Plus available from BYK-Gardner.Prior to fabrication of the embodiment 850, several APBF samples withprotective liners were subjected to 40° C. and 95% RH for 4 and 8 hours,respectively. Each of these samples, along with control samples of APBFstored under ambient conditions, was assembled with an EC-element,vacuum bagged, and autoclaved at 95° C. and 200 psi for about 1 hour toform mirror systems of the embodiment 850. The transmitted haze readingstaken after the fabrication of the embodiment and during the hightemperature storage test at 105° C. and at 24 hour intervals showed thatelevated pre-fabrication water content in APBF increases the haze levelsof the laminate up to 4 times. It was additionally showed thatpre-fabrication drying of the APBF samples under vacuum (e.g., at 40° C.and less than 50 torr pressure) removes the excess of water from theAPBFs, and results in the laminates that do not exhibit excessivetransmitted haze. Our study indicated that for long-term stability ofAPBF-containing laminates and mirror systems the APBF should preferablybe stored under relatively low humidity and levels of humidity should becontrolled during the lamination process. APBF-laminate-containingembodiments of the invention are characterized by transmitted hazelevels of less than 5%, more preferably less than 3%, and mostpreferably less than 1% as tested after high-temperature storage (e.g.,105° C. for 96 hours).

We found that fabrication, according to embodiments of the invention, ofAPBF-based laminates having high image-forming automotive opticalquality is consistent with but not necessarily limited to laminating anAPBF directly to a rigid optical substrate so as to provide asubstantially direct physical contact between at least one side of thefilm and a surface of a rigid optical substrate. Stated differently, weunexpectedly discovered that a laminate containing substantially no or aminimal amount of initially soft curable material such aspressure-sensitive adhesive (PSA) or other curable adhesive along atleast one lamination interface is very likely to satisfy the imagingquality requirements. We also found that simultaneous presence of someadhesive at both lamination interfaces (in the case of a laminatestructured according to FIG. 3(D), for example) the image-preservingreflecting properties of such laminate are more likely to be degraded.As a result, a rearview mirror assembly incorporating such a laminatewould be less likely to satisfy the existing optical quality standards.

We have also unexpectedly discovered that, for retaining a good mirrorquality after 48 hours of 105° C. storage, it may be beneficial toemploy embodiments of the APBF-containing laminates of the inventionwhere at least one side of the APBF is not be directly adhered to arigid substrate. That is, a laminate may be formed without a superstrateaccording to a general embodiment of FIG. 3(F) or, if an alternativeembodiment of FIG. 3(D) is used, the laminate may preferably include alayer of relatively pliable material, broadly defined asstress-relaxation means (such as flexible adhesive), between an APBF andonly one of the substrate and superstrate. In operation, a benefit ofusing a stress relaxation means stems from at least partial compensationof the differences in coefficients of thermal expansion (CTEs) betweenthe film and the substrate and/or superstrate. Generally, due to suchmismatch in CTEs, a laminate structured according to [G/RP/G] andexposed to elevated temperatures (e.g., during the storage test at 105°C.) acquires mechanical stresses resulting in visible degradation of theRP-film and substantial reduction of quality of the laminate. A stressrelaxation means, when present, may facilitate a relief of mechanicalstresses at elevated temperatures.

(2) Testing of Samples Employing UV-Protection Means.

The following provides examples of experimentally measured changes inreflected spectra of APBF-containing embodiments of the invention thatcorrespond to different UV attenuation means and methods. These testresults are for exposure to the weatherometer conditions utilizing lightsource, filters, Automatic irradiance, Black panel temperature, and Drybulb temperature of the light cycle of SAE J1885 (relative humidity wasnot controlled). One hour of exposure under these conditions correspondsto a radiant exposure of roughly 2 kJ/m² as it is calculated in varioustest requirements. For these examples the color values were measuredusing the CIE Standard D65 illuminant and a 2-degree observer.

Sample A of Table 16A included a DBEF-Q laminated between a surface ofthe 1.6 mm thick glass and a coated with opaque layer of Chromiumsurface of another lite of glass. The color change value ΔE*=6.67 aftertwo weeks of testing which was found to be excessive for automotivepurposes. Transmission spectra for 1.6 mm glass of the type used to makeSample A are shown in Table 16B and FIGS. 47(A,B).

Sample B of Table 16A included a DBEF-Q laminated between a surface ofthe glass prism and a coated with opaque layer of Chromium surface ofanother lite of glass. The corresponding color change value wasΔE*=11.37 after two weeks of testing which was found to be excessive forautomotive purposes. Transmission values for prism glass of the typeused to make Sample B were not measured.

Sample C of Table 16A included a DBEF-Q laminate between a surface ofglass containing a UV-blocking coating ClimaGuard-SPF® (from GuardianIndustries) and a coated with opaque layer of Chromium surface ofanother lite of glass. The color change value was, as shown in Table16A, ΔE*=1.99 after two weeks of testing, which is acceptable forautomotive purposes. Transmission values for used ClimaGuard® glass areshown in Table 16B and FIGS. 48(A,B).

Sample D of Table 16A included a DBEF-Q laminated between a treatedsurface of the Tru Vue Museum® glass (Tru Vue Inc.) and a coated withopaque layer of Chromium surface of another lite of glass. The colorchange value was ΔE*=2.50 after two weeks of testing, which isacceptable for automotive purposes. Transmission values for Tru VueMuseum® glass used are shown in Table 16B and FIGS. 48(A,B).

Sample E of Table 16A included a DBEF-Q laminate between a 1.6 mm-thickraw glass and a coated with opaque layer of Chromium surface of anotherlite of glass. In addition, a glass plate with an interferentialcoating, DSI Ultra Block™ (Deposition Sciences Inc), was placed in frontof the 1.6 mm raw glass as a filter. Sample E was exposed in theweatherometer with the filter plate in place, but color measurementswere taken with the filter plate removed. The measured color changevalue ΔE*=0.72 after 13 days of testing which is acceptable forautomotive purposes. Transmission values for DSI Ultra Block™ filterplate are shown in Table 16B and FIGS. 48(A,B).

Sample F of Table 16A included a DBEF-Q laminated between the UVblocking glass from China Building Materials Academy Quartz and SpecialGlasses Institute and a coated with opaque layer of Chromium surface ofanother lite of glass. The color change value was ΔE*=0.61 after 13 daysof testing which is acceptable for automotive applications. Transmissionvalues for glass of the type used to make Sample F are shown in Table16B and FIGS. 48(A,B).

Sample G of Table 16A included a DBEF-Q laminated between a piece ofSolarphire® (PPG Inc.) and an overcoated with a bi-layer (ruthenium ontop of chromium) surface of another lite of glass so as to have DBEF-Qand Ru-layers to be adjacent. The color change value was ΔE*=10.52 after13 days of testing which is too excessive for automotive applications.Transmission values for Solarphire® glass of the type used shown inTable 16C and FIGS. 47(A,B).

Sample H of Table 16A included a DBEF-Q laminated between Solarphire PV®(PPG Inc) and an overcoated with a bi-layer (ruthenium on top ofchromium) surface of another lite of glass so as to have DBEF-Q andRu-layers to be adjacent. The color change value was ΔE*=21.53 after 13days of testing which is excessive for automotive applications.Transmission values for Solarphire PV® glass of the type used are shownin Table 16C and FIGS. 47(A,B).

Sample I of Table 16A included a DBEF-Q laminated between Solarphire AR®(PPG Inc) and an overcoated with a bi-layer (ruthenium on top ofchromium) surface of another lite of glass so as to have DBEF-Q andRu-layers to be adjacent. The UV blocking coating of Solar4phire PV wasplaced towards the DBEF-Q. The color change value was ΔE*=2.78 after 13days of testing, which is acceptable for automotive applications.Transmission values for Solarphire AR® glass are shown in Table 16C andFIGS. 47A(,B).

Sample J of Table 16A included a 1.6 mm-thick raw glass laminated to 3MPSA 8172P (3M) laminated to DBEF-Q laminated to a coated with opaquelayer of Chromium lite of glass. The color change value was ΔE*=1.27after 13 days of testing which is acceptable for automotiveapplications. Transmission values for a laminate of 3M PSA 8172P and twopieces of 1.6 mm glass of the type used are shown in Table 16C and FIGS.49(A,B).

Sample K of Table 16A is of the construction of 1.6 mm raw glasslaminated to DBEF-Q which is laminated to coated glass where the layerin contact with the DBEF-Q is opaque chrome with the addition of GilaFade Control Clear (CP Films Inc) which was adhered to the front surfaceof the 1.6 mm glass top plate after the removal of the release liner.The color change value was ΔE*=2.16 after 13 days of testing which isacceptable for automotive applications. Transmission values for GilaFade Control Clear with PSA and release liner used are shown in Table16C and FIGS. 49(A,B).

Generally, in order to meet acceptable UV durability requirements in theJ1885 test, it is desirable to attenuate UV light at wavelengths shorterthan about 360 nm, preferably shorter than about 370 nm, more preferablyshorter than about 380 nm and most preferably shorter than about 390 nm.It is preferred to attenuate more than 50% of the targeted wavelengths,more preferably more than 70% and even more preferably more than about85%. One non-limiting criteria of sample acceptance is a color changevalue ΔE* that is less than 3 after 300 hours of the light on conditionof J1885 which is approximately 600 kJ/m² of exposure per thespecification.

TABLE 16A 1 Week 2 Weeks 3 Weeks Glass (Coating/Film) Type Δa* Δb* ΔE*Δa* Δb* ΔE* Δa* Δb* ΔE* A - 1.6 mm Raw Glass Laminate −0.46 2.45 2.51−1.13 6.42 6.67 −1.63 10.24 10.69 B - Prism (raw glass) Laminate −0.895.03 5.24 −1.61 11.04 11.37 −2.07 15.52 16.03 C - ClimaGuard SPF ®Laminate 0.05 1.69 1.75 −0.07 1.89 1.99 −0.15 2.11 2.19 D - Tru VueMuseum ® Laminate −1.03 1.12 1.63 −1.46 1.87 2.50 −1.59 2.28 2.86 1 Week13 Days 3 Weeks Glass/Coating/Film Type Δa* Δb* ΔE* Δa* Δb* ΔE* Δa* Δb*ΔE* E - DSI Ultra Block ™ Filter −0.06 0.02 0.62 −0.03 −0.02 0.72 F -China B.M.A. Laminate −0.08 0.42 0.66 −0.10 0.48 0.61 UV glass G -Solarphire ® Laminate −0.82 4.12 4.30 −1.67 10.09 10.52 H - SolarphirePV ® Laminate −2.11 12.24 12.72 −2.48 20.86 21.53 I - Solarphire AR ®Laminate −0.23 0.75 0.79 −0.47 2.65 2.78 J - 3M PSA 8172P Laminate 0.180.29 0.36 0.05 0.49 1.27 K - Gila Fade Control Filter 0.04 1.02 1.06−0.44 2.07 2.16

TABLE 16B Transmission (%) Wave- A - 1.6 mm C - Clima D - Tru Vue E -DSI F - China length Raw Guard Museum Ultra B.M.A. (nm) Glass SPF ®Glass ® Block ™ UV Glass 350.0 84.0% 0.3% 0.4% 0.3% 0.4% 361.2 88.1%0.4% 0.5% 0.3% 0.4% 370.7 89.0% 0.7% 1.1% 0.4% 0.5% 380.3 88.5% 2.6%4.0% 0.6% 0.9% 389.9 89.5% 12.8% 16.3% 1.8% 6.8% 399.5 90.0% 38.6% 42.6%5.5% 22.0% 410.8 90.1% 68.6% 71.5% 41.6% 43.7% 420.4 90.0% 80.8% 84.8%90.7% 58.9% 430.0 90.1% 86.2% 91.7% 92.2% 69.6% 439.6 90.1% 88.1% 95.1%92.6% 76.5% 450.8 90.4% 89.1% 97.4% 93.6% 81.2%

TABLE 16C Transmission (%) Wave- J - 3M K - Gila length G - H -Solarphire I - Solarphire 8172P Fade (nm) Solarphire ® PV ® AR ® PSAControl 350.0 46.2% 90.3% 11.6% 0.5% 0.3% 361.2 78.0% 91.2% 32.8% 0.7%0.4% 370.7 87.0% 91.6% 46.2% 1.3% 0.5% 380.3 89.6% 91.4% 57.0% 7.1% 1.1%389.9 90.6% 91.5% 66.9% 41.9% 7.9% 399.5 91.1% 91.6% 75.6% 76.1% 31.1%410.8 91.3% 91.6% 83.3% 86.4% 60.9% 420.4 91.3% 91.6% 87.5% 87.6% 70.6%430.0 91.3% 91.6% 89.9% 88.0% 73.5% 439.6 91.4% 91.7% 91.0% 88.2% 76.3%450.8 91.5% 91.7% 91.7% 88.7% 79.9%

Characterization of Optical Distortion Characteristics of ExemplaryEmbodiments.

Table 17 shows the samples of data representing characterization of theextended distortions and the resulting optical properties of variousembodiments of the invention. These results demonstrate that method ofthe invention allows for fabrication of embodiments that, as evidencedby SW, LW, Wa, Wb, We and Millidiopter readings, meet the opticalrequirements of the most demanding applications.

Characterizations were conducted with the use of wave-scan technique andby measuring the changes in optical power of the surface-under-test asdiscussed above. As shown, samples 1 through 3 represent inherentdistortions observed in original reflective polarizer materials, andsamples 4, 5, and 26 represent base-line distortions for a glasssubstrate, an EC-element having ITO-coatings on surfaces II and III, andan uncoated prism element, respectively. As other samples demonstrate,these inherent distortions may be compensated or reduced when thefabrication of a mirror system is carried out according to the processof the invention. In a case when the fabrication process is notadequately controlled, these inherent distortions may be magnified andtranslated into the final product. Samples 6 and 24 represent theproperties of an embodiment 2100 structured according to [G/PSA/DBEF],see FIG. 21(A), which has a PSA layer 2030 between the glass plate 826and the APBF 824 and the superstrate released. Samples 6 and 24 werefabricated without and with autoclaving, respectively. The laminationprocess carried out under substantially omnidirectional pressureresulted in significant improvement of the SW figures in the finallaminate, but at the same time increased the LW values. The Wa, Wb andWe were also generally higher for sample 24 compared to sample 6.Samples 7 and 20 were structured according to [G/PSA/DBEF/G], seeembodiment 2110 of FIG. 21(B), which is a laminate having both thesubstrate and superstrate. Samples 7 and 20 were fabricated with andwithout autoclaving, respectively. As can be seen from comparison ofsamples 6, 24 with samples 7, 20, the reduction of distortioncharacteristics of a laminate substantially relates not only to the useof omnidirectional pressure during the fabrication of the laminate, butalso to having the RP-layer of the laminate being supported by glasslites on both sides. This correlates with the findings discussed abovein reference to Tables 11 through 16. The Wa, Wb and We numbers are allsubstantially improved with autoclaving (sample 20) and are all lessthan 3.0. Samples 8 and 19 correspond to the embodiment of FIG. 8(C),fabricated without and with autoclaving, respectively. Both thewave-scan test and the optical power test demonstrate substantialreduction of extended distortions as a result of autoclaving procedure.The autoclaving procedure is shown to reduce the aggregate distortionsin the samples, as evidenced by Wa, Wb and We readings that are all lessthan 3. Similar results have been obtained for samples 9 and 25, whichcorresponded to the embodiment 836 of FIG. 8(D), fabricated without andwith autoclaving, respectively. Each of samples 8, 19, 9, and 25 usedDBEF-Q film as a reflective polarizer. Characterization of samples 11and 13, each of which included prismatic elements, demonstratedsubstantial lack of extended distortion. Here, both metrics (Wa, Wb andWc) and (SW, LW) are quire low demonstrating that the parts aresubstantially free of objectionable distortions. Samples 14, 15, 16, and17 represented the use of APBF different from the DBEF-Q product by 3MInc. In particular, sample 14 was structured according to the embodiment850 of FIG. 8(F) and utilized the APF 35 film as a reflective polarizer824. Sample 15 represented a laminate-containing mirror structuredepicted in an embodiment 2400 of FIG. 24. The embodiment 2400schematically illustrates a laminate of the invention, wherein theanisotropic film APF 35 used as a RP 824 is laminated between theEC-element 840 and a third light of glass 610 having an OREL coatingdeposited on surface V. In this embodiment, the OREL coating includes a50 nm layer 2410 of Chromium and a 20 nm layer 2420 of Ruthenium. Sample16 represented the embodiment 884 of FIG. 8(I) with APF 50 as areflective polarizer 824. Sample 17 also corresponded to FIG. 8(I), bututilized APF 50 as a reflective polarizer. Although samples 14 through17 show variable levels of distortions and are all acceptable for use inmost of automotive application, the distortions of sample 16 appear tobe particularly low. DBEF-Q was used as an RP in sample 21 structuredaccording to the embodiment 884 of 8(I). Samples 27 generallycorresponded to the embodiment 884 of FIG. 8(I). Sample 28 correspondedto an embodiment 2200 of FIG. 22 where, in comparison with theembodiment 884 of FIG. 8(I), the PSA layer 2030 has been disposedbetween the RP 824 and glass plate 610. Both samples demonstratesubstantial lack of extended distortions (characterized by SW and LWvalues) and excellent optical properties. Additionally, all three ofthese examples had excellent Wa, Wb and We values suitable for even themost stringent applications.

TABLE 17 # Sample Description SW LW Wa Wb Wc Millidiopters 1 OriginalAPF 35 film 13.2 13.8  9.7 13.4 4 2 Original APF 50 film 17.9  5.2 10.625.1 8.8 3 Original DBEF-Q film  6.4  7.3  2.4  7.6 5.5 4 A glasssubstrate  0  0  2.55  2.35 0.05 81 . . . 141 5 An EC-element with ITO 0  0.2  2  1.8 0.1 156 . . . 227 coatings on surfaces II and III 26 Anuncoated glass prism 0.1 . . . 0.2  0  2.0  2.5 0.1 6 Embodiment 2100 ofFIG. 4.4 . . . 8.6 1.5 . . . 3.1 3.3 . . . 4.0 6.3 . . . 9.4 2.9 . . .5.5 174 . . . 204 21(A), no autoclaving used 24 Embodiment 2100 of FIG. 2.7 4.7 . . . 4.9 12.5  6.8 5.5 21(A), with autoclaving 7 Embodiment2110 of FIG.  5.7 21.9  3.7  8.7 4.8 227 . . . 1,104 21(B), noautoclaving used. 20 Embodiment 2110 of FIG. 1.2 . . . 1.3 0.8 . . . 0.92.3 . . . 2.5 2.2 . . . 2.9 0.9 . . . 1.0 235 . . . 552 21(B), withautoclaving 8 Embodiment 830 of FIG. 1.6 . . . 3.7 6.1 . . . 16.1 3.2 .. . 4.3 6.3 . . . 8.5 3.3 . . . 5.1 432 . . . 2,100 8(C), no autoclavingused 19 Embodiment 830 of FIG. 1.4 . . . 2.5 0.8 . . . 0.9 1.5 . . . 2.42.4 . . . 3.9 0.9 . . . 1.4 208 . . . 257 8(C), with autoclaving 11Embodiment 410 of FIG. 1 . . . 1.5 0.6 . . . 0.9 2.0 . . . 3.2 2.3 . . .4.0 0.6 4(C) 13 Embodiment 2300 of FIG. 0 . . . 2.2 0.1 . . . 1 2.1 . .. 2.5 2.8 . . . 3.9 0.8 23, with DBEF-Q as a reflective polarizer 14Embodiment 850 of FIG. 4.8 . . . 5.1  0.4  5.2  8.8 0.6 295 . . . 4768(F), with APF 35 as reflective polarizer 15 FIG. 2400 of FIG. 24, with2.4 . . . 4.9 0.9 . . . 1.0 3.7 . . . 5.3 4.5 . . . 8.1 0.4 . . . 0.5327 . . . 375 APF 35 as a reflective polarizer 16 Embodiment 884 of FIG.0.1 . . . 0.2  0.1 1.2 . . . 1.4 0.9 . . . 1.1 0.0 . . . 0.1 285 . . .361 8(I), with APF 35 as reflective polarizer 17 Embodiment 884 of FIG.8.7 . . . 9.8  0.6 6.8 . . . 8.0 13.6 . . . 14.0 1.1 . . . 1.6 527 . . .1,722 8(I), with APF 50 as reflective polarizer 21 Embodiment 884 ofFIG. 0.6 . . . 1.2 0.5 . . . 2.4 1.1 . . . 1.9 1.2 . . . 2.6 0.5 . . .0.8 250 . . . 592 8(I), with DBEF-Q as reflective polarizer 27Embodiment 884 of FIG. 0.7 . . . 1.2 0.8 . . . 1.7 1.1 . . . 2.0 1.1 . .. 2.2 0.4 . . . 0.8 8(I), with DBEF-Q as opaque opaque Opaque OpaqueOpaque reflective polarizer zone; zone; zone; zone; zone; 1.6 . . . 1.70.4 . . . 0.6 1.2 . . . 1.5 2.3 . . . 2.6 0.7 . . . 0.8 transfl zonetransfl transfl transfl transfl zone zone zone zone 28 Embodiment 2200of FIG. 0.5 . . . 0.8 0.4 . . . 1.7 1.3 . . . 2.7 1.1 . . . 2.7 0.5 . .. 0.6 22, with DBEF-Q as reflective polarizer

Generally, embodiments of the invention may be configured to define aconvex element, an aspheric element, a planar element, a non-planarelement, an element having a wide FOV, or a combination of these variousconfigurations in different areas to define a mirror element withgenerally complex shape. In case of an electrochromic rearview mirrorassembly, the first surface of the first substrate may comprise ahydrophilic or hydrophobic coating to improve the operation. Theembodiments of the reflective elements may comprise an anti-scratchlayer on the exposed surfaces of at least one of the first and secondsubstrates. Examples of various reflective elements are described inU.S. Pat. Nos. 5,682,267, 5,689,370, 5,825,527, 5,940,201, 5,998,617,6,020,987, 6,037,471, 6,057,956, 6,062,920, 6,064,509, 6,111,684,6,166,848, 6,193,378, 6,195,194, 6,239,898, 6,246,507, 6,268,950,6,356,376, 6,441,943, and 6,512,624. The disclosure of each of thesepatents is incorporated herein in its entirety by reference.

Electrochromic mirror assemblies utilizing embodiments of the presentinvention contain an electrochromic medium that is preferably capable ofselectively attenuating light traveling therethrough and preferably hasat least one solution-phase electrochromic material and preferably atleast one additional electroactive material that may be solution-phase,surface-confined, or one that plates out onto a surface. However, thepresently preferred media are solution-phase redox electrochromics, suchas those disclosed in commonly assigned U.S. Pat. Nos. 4,902,108,5,128,799, 5,278,693, 5,280,380, 5,282,077, 5,294,376, 5,336,448,5,808,778 and 6,020,987. The entire disclosure of each of these patentsis incorporated herein in by reference. If a solution-phaseelectrochromic medium is utilized, it may be inserted into the chamberthrough a sealable fill port through well-known techniques, such asvacuum backfilling and the like. In addition, the disclosure of each ofU.S. Pat. Nos. 6,594,066, 6,407,847, 6,362,914, 6,353,493, 6,310,714 isincorporated herein by reference in its entirety.

Electrochromic medium preferably includes electrochromic anodic andcathodic materials that can be grouped into the following categories:

(i) Single Layer:

The electrochromic medium is a single layer of material that may includesmall inhomogeneous regions and includes solution-phase devices where amaterial is contained in solution in the ionically conductingelectrolyte and remains in solution in the electrolyte whenelectrochemically oxidized or reduced. U.S. Pat. No. 6,193,912 entitled“NEAR INFRARED-ABSORBING ELECTROCHROMIC COMPOUNDS AND DEVICES COMPRISINGSAME”; U.S. Pat. No. 6,188,505 entitled “COLOR STABILIZED ELECTROCHROMICDEVICES”; U.S. Pat. No. 6,262,832 entitled “ANODIC ELECTROCHROMICMATERIAL HAVING A SOLUBLIZING MOIETY”; U.S. Pat. No. 6,137,620 entitled“ELECTROCHROMIC MEDIA WITH CONCENTRATION ENHANCED STABILITY PROCESS FORPREPARATION THEREOF AND USE IN ELECTROCHROMIC DEVICE”; U.S. Pat. No.6,195,192 entitled “ELECTROCHROMIC MATERIALS WITH ENHANCED ULTRAVIOLETSTABILITY”; U.S. Pat. No. 6,392,783 entitled “SUBSTITUTED METALLOCENESFOR USE AS AN ANODIC ELECTROCHROMIC MATERIAL AND ELECTROCHROMIC MEDIAAND DEVICES COMPRISING SAME”; and U.S. Pat. No. 6,249,369 entitled“COUPLED ELECTROCHROMIC COMPOUNDS WITH PHOTOSTABLE DICATION OXIDATIONSTATES” disclose anodic and cathodic materials that may be used in asingle layer electrochromic medium, the entire disclosures of which areincorporated herein by reference. Solution-phase electroactive materialsmay be contained in the continuous solution phase of a cross-linkedpolymer matrix in accordance with the teachings of U.S. Pat. No.5,928,572, entitled “IMPROVED ELECTROCHROMIC LAYER AND DEVICESCOMPRISING SAME” or International Patent Application No. PCT/US98/05570entitled “ELECTROCHROMIC POLYMERIC SOLID FILMS, MANUFACTURINGELECTROCHROMIC DEVICES USING SUCH SOLID FILMS, AND PROCESSES FOR MAKINGSUCH SOLID FILMS AND DEVICES,” and U.S. patent application Ser. No.11/272,552 titled “Electrochromic Compounds and Associated Media andDevices and filed Nov. 10, 2005. The disclosure of each of these patentdocuments is incorporated herein in its entirety by reference.

The entire disclosure of each of the U.S. patent application Ser. No.12/284,701, filed Sep. 24, 2008, entitled ULTRAVIOLET LIGHT STABILIZINGCOMPOUNDS AND ASSOCIATED MEDIA AND DEVICES, U.S. Pat. No. 7,428,091entitled ELECTROCHROMIC COMPOUNDS AND ASSOCIATED MEDIA AND DEVICES, andU.S. Pat. No. 7,256,924 entitled MULTI-CELL ELECTROCHROMIC DEVICES,disclosing additional teachings related to the EC-element, isincorporated herein by reference in its entirety.

At least three electroactive materials, at least two of which areelectrochromic, can be combined to give a pre-selected color asdescribed in U.S. Pat. No. 6,020,987 entitled “ELECTROCHROMIC MEDIUMCAPABLE OF PRODUCING A PRE-SELECTED COLOR,” the entire disclosure ofwhich is incorporated herein by reference. This ability to select thecolor of the electrochromic medium is particularly advantageous whendesigning information displays with associated elements.

The anodic and cathodic materials can be combined or linked by abridging unit as described in International Application No.PCT/WO97/EP498 entitled “ELECTROCHROMIC SYSTEM,” the entire disclosureof which is incorporated herein by reference. It is also possible tolink anodic materials or cathodic materials by similar methods. Theconcepts described in these applications can further be combined toyield a variety of electrochromic materials that are linked.

Additionally, a single layer medium includes the medium where the anodicand cathodic materials can be incorporated into the polymer matrix asdescribed in International Application No. PCT/WO98/EP3862 entitled“ELECTROCHROMIC POLYMER SYSTEM,” U.S. Pat. No. 6,002,511, orInternational Patent Application No. PCT/US98/05570 entitled“ELECTROCHROMIC POLYMERIC SOLID FILMS, MANUFACTURING ELECTROCHROMICDEVICES USING SUCH SOLID FILMS, AND PROCESSES FOR MAKING SUCH SOLIDFILMS AND DEVICES,” the entire disclosures of which are incorporatedherein by reference.

Also included is a medium where one or more materials in the mediumundergoes a change in phase during the operation of the device, forexample, a deposition system where a material contained in solution inthe ionically conducting electrolyte which forms a layer, or partiallayer on the electronically conducting electrode when electrochemicallyoxidized or reduced.

(ii) Multilayer:

The medium is made up in layers and includes at least one materialattached directly to an electronically conducting electrode or confinedin close proximity thereto which remains attached or confined whenelectrochemically oxidized or reduced. Examples of this type ofelectrochromic medium are the metal oxide films, such as tungsten oxide,iridium oxide, nickel oxide, and vanadium oxide. A medium, whichcontains one or more organic electrochromic layers, such aspolythiophene, polyaniline, or polypyrrole attached to the electrode,would also be considered a multilayer medium.

In addition, the electrochromic medium may also contain other materials,such as light absorbers, light stabilizers, thermal stabilizers,antioxidants, thickeners, or viscosity modifiers.

It may be desirable to incorporate a gel into the electrochromic deviceas disclosed in commonly assigned U.S. Pat. No. 5,940,201 entitled “ANELECTROCHROMIC MIRROR WITH TWO THIN GLASS ELEMENTS AND A GELLEDELECTROCHROMIC MEDIUM”. The entire disclosure of this U.S. patent isincorporated herein by reference.

In at least one embodiment of a rearview mirror assembly utilizing amirror element according to the present invention, the rearview mirrorassembly is provided with an electro-optic element having asubstantially transparent seal. Examples of EC-structures, substantiallytransparent seals and methods of forming substantially transparent sealsare provided in U.S. Pat. No. 5,790,298, the entire disclosure of whichis included herein by reference. U.S. Pat. Nos. 6,665,107, 6,714,334,6,963,439, 6,195,193, 6,157,480, 7,190,505, 7,414,770, and U.S. patentapplication Ser. No. 12/215,712 disclose additional subject matterrelated to seals and seal materials. The disclosure of each of thesesdocuments is incorporated herein by reference in its entirety.

In at least one embodiment, a mirror structure according to theinvention or a rearview mirror assembly utilizing such mirror structuremay include a spectral filter material and/or a bezel for protecting theassociated seal from damaging light rays and to provide an aestheticallypleasing appearance. Examples of various bezels are disclosed, e.g., inU.S. Pat. Nos. 5,448,397, 6,102,546, 6,195,194, 5,923,457, 6,238,898,6,170,956 and 6,471,362, the disclosure of each of which is incorporatedherein in its entirety by reference.

As discussed above, in at least one embodiment, an embodiment of theAPBF-containing laminate of the invention can be used in conjunctionwith a display such as an RCD, or another light source such as onegenerated polarized light, for example a laser source. Discussion ofvarious displays that can be used with embodiments of the invention isprovided, e.g., in U.S. Provisional Application No. 60/780,655 filed onMar. 9, 2006; U.S. Provisional Application No. 60/804,351 filed on Jun.9, 2006; U.S. Patent Application Publication Nos. 2008/0068520, U.S.Pat. No. 7,221,363; and U.S. patent application Ser. Nos. 11/179,798 and12/193,426. The entire disclosure of each of these applications isincorporated herein by reference. Generally, a light source can bedisposed as a stand-alone component separated from the mirror structureor it can be in physical contact with the mirror structure. Anembodiment of the laminate of the invention can also be beneficiallyused in applications utilizing rear-projection displays utilizing lasersources, e.g. a rear-projection display by Mitsubishi Corporationdescribed at www.lasertvnews.com/features.asp.

In at least one of embodiments, a mirror structure including anAPBF-based laminate of the invention may be configured in a rearviewmirror assembly that may include a glare light sensor or an ambientlight sensor, which are described in commonly assigned U.S. Pat. Nos.6,359,274 and 6,402,328. The disclosure of each of these patents isincorporated herein by reference in its entirety. The electrical outputsignal from either or both of these sensors may be used as inputs to acontroller on a circuit board of the assembly that controls theintensity of display backlighting. The details of various controlcircuits for use herewith are described in commonly assigned U.S. Pat.Nos. 5,956,012; 6,084,700; 6,222,177; 6,224,716; 6,247,819; 6,249,369;6,392,783; and 6,402,328, the disclosures of which are incorporated intheir entireties herein by reference. In addition or alternatively, therearview mirror assembly may include at least one additional device suchas, without limitation, an interior illumination assembly, a voiceactivated system, a trainable transceiver, a microphone, a compasssystem, a digital sound processing system, a highway toll boothinterface, a telemetry system, a moisture sensor, a global positioningsystem, a vehicle vision system, a wireless communication interface, acamera, a transflective reflector, a navigation system, a turn signal,and an adaptive cruise control system. These systems may be integrated,at least in part, in a common control with information displays and/ormay share components with the information displays. In addition, thestatus of these systems and/or the devices controlled thereby may bedisplayed on the associated information displays.

The embodiments of the invention described above are intended to bemerely exemplary; numerous variations and modifications will be apparentto those skilled in the art.

Examples of Modifications.

It is understood that an APBF-containing embodiment of the invention maybe structured as any of multi-zone EC-reflectors disclosed in theMulti-Zone Mirror Application. Any such embodiment will contain variousoptical thin-film layers described therein that enhance the performanceof the multi-zone mirror system of the invention. In particular, any ofthe multi-zone reflector embodiments described in the Multi-Zone MirrorApplication—be it an embodiment utilizing an abrupt transition betweenthe opaque and transflective zones of the mirror element, such as, e.g.,one of the embodiments described in reference to FIG. 5 through FIG. 8of the Multi-Zone Mirror Application, or an embodiment utilizing agradual transition between the opaque and transflective zones of themirror element, such as, e.g. one of the embodiments described inreference to FIG. 9 through FIG. 15 of the Multi-Zone MirrorApplication—may be configured as part of the rearview mirror assemblyaccording to the general principle illustrated in FIG. 18 herein. Itwill be understood that, in any of such possible configurations, an APBFelement may be appropriately disposed between a display 1850 and amulti-zone mirror element 1820, as part of the auxiliary optics 1830, inany of the positions described herein, whether as a stand-alonecomponent or a component laminated between other functional elements ofthe assembly.

It is also understood that UV-protection of the polymer-based RPcomponent of the embodiments discussed above may be achieved withoutemploying additional UV-blocking agents but through the use ofappropriately designed reflectance-enhancing layers. The followingExamples A and B illustrate the performance of some thin-films coatingsthat, when employed in front of an APBF in one of embodiments of theinvention, may allow for simultaneous optimization ofreflectance-enhancement of a mirror system of the invention andminimization of transmission of UV-light through the stacks towards theAPBF. Optical constants for materials used to simulate the performanceof these coatings (with a reference wavelength of 250 nm and azero-degree angle of incidence) are presented in FIG. 37.

Example A

Table 23 lists design parameters of a thin-film stack on a glasssubstrate, while FIG. 38 shows a dispersion of reflectance andtransmittance characteristics for this stack. The overall reflectancevalue for unpolarized light is about 35% in the visible range, while thetransmittance nears zero below approximately 380 nm.

Example B

Design parameters for this alternative stack on a glass substrate,affording an approximately 45% reflectance in the visible spectralregion and reduced transmittance at wavelengths below 400 nm as shown inFIG. 39, are illustrated in Table 24.

Example C

Design parameters for this alternative stack on a glass substrate,affording an approximately 45% reflectance in the visible spectralregion but providing improvement in UV-blocking as compared to thecoating of Example B, as evidenced by FIG. 40, are shown in Table 25.

In comparison with Examples A and B, Example D illustrates a design of athin-film coating that not only has UV-blocking andreflectance-enhancing properties but is also tailored to provide forpreferentially high transmittance values in RGB-bands where a colordisplay, located behind a mirror system of the invention, may operate.For the purpose of this example, the “blue” wavelength pass-band isdefined by a 440-460 nm region, the “green” pass-band is defined as a540-560 nm region, and a “red” pass-band is defined as a 630-660 nmregion. Design parameters for this coating, deposited on a glasssubstrate, are listed in Table 26, and some optical characteristics oflight (D 65, CIE 1964 observer) incident on this coating at zero degreesare shown in FIG. 41 and Table 27.

The following additional Examples E and F pertain to the use ofreflectance-enhancing coatings of the Examples B and D, respectively, ina transflective zone of a specific embodiment. This specific embodimentcomprises, in the order viewed by the observer: 1) a 1.6 mm-thick firstglass substrate with an ITO layer (150 nm) deposited on surface II, 2)an EC-medium (150 nm), 3) a 1.6 mm-thick second glass substrate with anITO layer (150 nm) deposited on surface II, and 4) an APBF (DBEF-Q)laminated within the transflective zone between surface IV (of thesecond substrate) and surface V (of a 1.1 mm thick third lite of glass)that is overcoated with a reflectance-enhancing coating. In particular,in Example E, the reflectance-enhancing coating deposited on surface Vis that from Example B. The transmission characteristics of theresulting embodiment are shown in FIG. 42, and the color characteristicsare listed in Table 28. Example F corresponds to the situation when thereflectance-enhancing coating deposited on surface V of theabove-mentioned embodiment is that from Example D. Opticalcharacteristics of the embodiment of this example are shown in FIG. 43and Table 29. Comparison between the transmittance characteristics ofthe embodiments of Example E and Example F are presented in FIG. 44.

Example G corresponds to a transflective zone of an embodiment thatincludes, in the order viewed by the observer: 1) a 1.6 mm-thick firstglass substrate with an ITO layer (150 nm) deposited on surface II, 2)an EC-medium (150 nm), 3) a 1.6 mm-thick second glass substrate with anITO layer (150 nm) deposited on surface II, and 4) an APBF (DBEF-Q)laminated within the transflective zone between surface IV (of thesecond substrate) and an uncoated surface V of a 1.1 mm-thick third liteof glass. The optical characteristics of such a design are shown inTable 30. A comparison among the Examples E and F and Example G, all ofwhich included a reflectance-enhancing coating containing forty threethin-film layers, illustrates the improvement in reflectancecharacteristics. Furthermore, Example F simultaneously attains UVblocking, reflectance enhancement and transmittance enhancement in thelight bands of LCD. It is understood that by appropriately designing thecoatings a UV blocking function may be removed from Examples D and F,leaving the coating to demonstrate reflectance enhancement andtransmittance enhancement only.

The influence of material absorption on optical characteristics of theoverall mirror system is illustrates in additional Examples H, I, and J.In particular, Example H provides a value for eye-weighed absorption ofambient light that has traversed a glass substrate and a half-wave-thickITO coating deposited on one of the substrate's surfaces. Example Iprovides a value for eye-weighed absorption of ambient light that hastraversed an EC-element comprising an EC-medium placed between two glasssubstrates each having one surface overcoated with a half-waveITO-layer. Finally, Example J demonstrates eye-weighed values forpolarized transmittance and unpolarized reflectance of the embodiment ofExample G. Calculations of all values thus defined were done fordifferent thicknesses of glass substrates and different absorbancevalues (calculated using appropriately scaled coefficients of extinctionof the ITO material), as indicated in Table 31. The eye-weighing hasbeen performed in the range between approximately 360 nm and 750 nm. Theresults in Table 31 clearly demonstrate the benefit of using anelectrooptic element having a low absorption front of the APBF. Theamount of light absorption that is acceptable in a particular embodimentmay vary. Preferably, the electrooptic element will have an absorptionless than 10%, more preferably less than 5% and most preferably lessthan 2.5%. RELs may not be needed if the absorption is properlycontrolled, or the RELs may contain fewer layers thus simplifying theoverall structure of the assembly and reducing costs.

TABLE 23 (Example A). Design: uv block with vis enhance2 ReferenceWavelength (nm): 250 Incident Angle (deg): 0 Refractive ExtinctionOptical Physical Layer Material Index Coefficient Thickness (QWOT)Thickness (nm) Medium Air 1 0 1 TiO2 3.73402 0.73131 0.35236347 5.9 2SiO2 1.50756 0 1.99557338 82.73 3 TiO2 3.73402 0.73131 0.69643061 11.664 SiO2 1.50756 0 0.55338444 22.94 5 TiO2 3.73402 0.73131 0.02764588 0.466 SiO2 1.50756 0 1.54587378 64.09 7 TiO2 3.73402 0.73131 0.64552373 10.88 SiO2 1.50756 0 2.1155252 87.71 9 TiO2 3.73402 0.73131 0.15882851 2.6610 SiO2 1.50756 0 0.77688382 32.21 11 TiO2 3.73402 0.73131 0.8645547414.47 12 SiO2 1.50756 0 0.70251929 29.12 13 TiO2 3.73402 0.731311.21048825 20.26 14 SiO2 1.50756 0 1.48678272 61.64 15 TiO2 3.734020.73131 0.03674043 0.61 16 SiO2 1.50756 0 1.49555366 62 17 TiO2 3.734020.73131 1.50389386 25.17 18 SiO2 1.50756 0 0.55062046 22.83 19 TiO23.73402 0.73131 0.9918027 16.6 20 SiO2 1.50756 0 0.82687503 34.28 21TiO2 3.73402 0.73131 0.61261152 10.25 22 SiO2 1.50756 0 1.49375953 61.9323 TiO2 3.73402 0.73131 0.59469162 9.95 24 SiO2 1.50756 0 1.3735843356.95 25 TiO2 3.73402 0.73131 0.10176567 1.7 26 SiO2 1.50756 01.24006099 51.41 27 TiO2 3.73402 0.73131 0.38900365 6.51 28 SiO2 1.507560 1.93868082 80.37 29 TiO2 3.73402 0.73131 0.13721662 2.3 30 SiO21.50756 0 0.73949159 30.66 31 TiO2 3.73402 0.73131 1.11326501 18.63 32SiO2 1.50756 0 1.1366994 47.13 33 TiO2 3.73402 0.73131 0.02080969 0.3534 SiO2 1.50756 0 1.08443578 44.96 35 TiO2 3.73402 0.73131 0.8904329514.9 36 SiO2 1.50756 0 1.48167627 61.43 37 TiO2 3.73402 0.731311.19582078 20.02 38 SiO2 1.50756 0 0.98396442 40.79 39 TiO2 3.734020.73131 0.45031072 7.54 40 SiO2 1.50756 0 4.07109085 168.78 41 TiO23.73402 0.73131 0.71878669 12.03 42 SiO2 1.50756 0 1.46325333 60.66 43TiO2 3.73402 0.73131 0.61115184 10.23 Substrate Float Glass 1.578570.00006 Total Thickness 1427.63 nm

TABLE 24 (Example B). Design: Design9 Reference Wavelength (nm): 250Incident Angle (deg): 0 Refractive Extinction Optical Physical LayerMaterial Index Coefficient Thickness (QWOT) Thickness (nm) Medium Air 10 1 TiO2 3.73402 0.73131 0.34773154 5.82 2 SiO2 1.50756 0 2.0074027283.22 3 TiO2 3.73402 0.73131 0.71244582 11.92 4 SiO2 1.50756 00.59650276 24.73 5 TiO2 3.73402 0.73131 0.04842828 0.81 6 SiO2 1.50756 01.55752757 64.57 7 TiO2 3.73402 0.73131 0.71180889 11.91 8 SiO2 1.507560 2.1456861 88.96 9 TiO2 3.73402 0.73131 0.1550899 2.6 10 SiO2 1.50756 00.79393713 32.91 11 TiO2 3.73402 0.73131 0.84344363 14.12 12 SiO21.50756 0 0.65441529 27.13 13 TiO2 3.73402 0.73131 1.29501365 21.68 14SiO2 1.50756 0 1.49801329 62.1 15 TiO2 3.73402 0.73131 0.0382956 0.64 16SiO2 1.50756 0 1.49189184 61.85 17 TiO2 3.73402 0.73131 1.63198813 27.3218 SiO2 1.50756 0 0.30009032 12.44 19 TiO2 3.73402 0.73131 1.0337000217.3 20 SiO2 1.50756 0 0.89649568 37.17 21 TiO2 3.73402 0.731310.54935807 9.2 22 SiO2 1.50756 0 1.5295528 63.41 23 TiO2 3.73402 0.731310.71687773 12 24 SiO2 1.50756 0 1.39735622 57.93 25 TiO2 3.73402 0.731310.15601681 2.61 26 SiO2 1.50756 0 1.26711596 52.53 27 TiO2 3.734020.73131 0.39272565 6.57 28 SiO2 1.50756 0 1.98850216 82.44 29 TiO23.73402 0.73131 0.20598867 3.45 30 SiO2 1.50756 0 0.76170969 31.58 31TiO2 3.73402 0.73131 1.25336544 20.98 32 SiO2 1.50756 0 1.20118763 49.833 TiO2 3.73402 0.73131 0.04283731 0.72 34 SiO2 1.50756 0 1.1430225747.39 35 TiO2 3.73402 0.73131 0.81443412 13.63 36 SiO2 1.50756 01.49211396 61.86 37 TiO2 3.73402 0.73131 1.26002182 21.09 38 SiO21.50756 0 0.9831479 40.76 39 TiO2 3.73402 0.73131 0.45252597 7.57 40SiO2 1.50756 0 4.09859593 169.92 41 TiO2 3.73402 0.73131 0.7977614113.35 42 SiO2 1.50756 0 1.48017738 61.36 43 TiO2 3.73402 0.731310.64129521 10.73 Substrate Glaverbel 1.57857 0.00006 Total Thickness1450.09 nm

TABLE 25 (Example C). Design: uv block with vis enhance example 4Reference Wavelength (nm): 250 Incident Angle (deg): 0 RefractiveExtinction Optical Physical Layer Material Index Coefficient Thickness(QWOT) Thickness (nm) Medium Air 1 0 1 TiO2 3.73402 0.73131 0.348879865.84 2 SiO2 1.50756 0 2.00414015 83.09 3 TiO2 3.73402 0.73131 0.7303545712.22 4 SiO2 1.50756 0 0.57601583 23.88 5 TiO2 3.73402 0.731310.03964011 0.66 6 SiO2 1.50756 0 1.48776774 61.68 7 TiO2 3.73402 0.731310.73697209 12.34 8 SiO2 1.50756 0 2.11451864 87.66 9 TiO2 3.734020.73131 0.12787617 2.14 10 SiO2 1.50756 0 0.75325055 31.23 11 TiO23.73402 0.73131 0.86994384 14.56 12 SiO2 1.50756 0 0.64830262 26.88 13TiO2 3.73402 0.73131 1.31859059 22.07 14 SiO2 1.50756 0 1.45803687 60.4515 TiO2 3.73402 0.73131 0.04370379 0.73 16 SiO2 1.50756 0 1.4728131561.06 17 TiO2 3.73402 0.73131 1.74248552 29.17 18 SiO2 1.50756 00.29584364 12.27 19 TiO2 3.73402 0.73131 0.98415294 16.47 20 SiO21.50756 0 0.92665976 38.42 21 TiO2 3.73402 0.73131 0.62430475 10.45 22SiO2 1.50756 0 1.53922062 63.81 23 TiO2 3.73402 0.73131 0.71809672 12.0224 SiO2 1.50756 0 1.34959527 55.95 25 TiO2 3.73402 0.73131 0.15802942.65 26 SiO2 1.50756 0 1.22149353 50.64 27 TiO2 3.73402 0.731310.41478337 6.94 28 SiO2 1.50756 0 1.93595747 80.26 29 TiO2 3.734020.73131 0.00149092 0.02 30 SiO2 1.50756 0 0.68213084 28.28 31 TiO23.73402 0.73131 1.26372564 21.15 32 SiO2 1.50756 0 1.11936985 46.41 33TiO2 3.73402 0.73131 0.01072272 0.18 34 SiO2 1.50756 0 1.16437308 48.2735 TiO2 3.73402 0.73131 0.87218427 14.6 36 SiO2 1.50756 0 1.5366260663.71 37 TiO2 3.73402 0.73131 1.19725742 20.04 38 SiO2 1.50756 01.03802074 43.03 39 TiO2 3.73402 0.73131 0.35117163 5.88 40 SiO2 1.507560 3.99469639 165.61 41 TiO2 3.73402 0.73131 0.88632161 14.84 42 SiO21.50756 0 1.40222652 58.13 43 TiO2 3.73402 0.73131 0.71925322 12.04Substrate Glaverbel 1.57857 0.00006 Total Thickness 1427.72 nm

TABLE 26 (Example D). Design: uv block with vis enhance and LCD bandpassexample 5 Reference Wavelength (nm): 250 Incident Angle (deg): 0Refractive Extinction Optical Physical Layer Material Index CoefficientThickness (QWO) Thickness (n) Medium Air 1 0 1 TiO2 3.73402 0.731310.42447154 7.1 2 SiO2 1.50756 0 2.30471572 95.55 3 TiO2 3.73402 0.731311.01606977 17.01 4 SiO2 1.50756 0 0.29323852 12.16 5 TiO2 3.734020.73131 0.22061093 3.69 6 SiO2 1.50756 0 1.15562624 47.91 7 TiO2 3.734020.73131 0.63633503 10.65 8 SiO2 1.50756 0 1.96198713 81.34 9 TiO23.73402 0.73131 0.13955544 2.34 10 SiO2 1.50756 0 0.79184418 32.83 11TiO2 3.73402 0.73131 1.13362253 18.97 12 SiO2 1.50756 0 0.88470124 36.6813 TiO2 3.73402 0.73131 1.33545495 22.35 14 SiO2 1.50756 0 1.3942761657.8 15 TiO2 3.73402 0.73131 0.0694175 1.16 16 SiO2 1.50756 0 1.1686534548.45 17 TiO2 3.73402 0.73131 1.52592119 25.54 18 SiO2 1.50756 00.36730127 15.23 19 TiO2 3.73402 0.73131 1.1185282 18.72 20 SiO2 1.507560 0.80871772 33.53 21 TiO2 3.73402 0.73131 0.75516097 12.64 22 SiO21.50756 0 1.88371402 78.09 23 TiO2 3.73402 0.73131 0.97266665 16.28 24SiO2 1.50756 0 1.35988907 56.38 25 TiO2 3.73402 0.73131 0.35608147 5.9626 SiO2 1.50756 0 1.13784244 47.17 27 TiO2 3.73402 0.73131 0.351883245.89 28 SiO2 1.50756 0 2.09278061 86.76 29 TiO2 3.73402 0.731310.51731663 8.66 30 SiO2 1.50756 0 0.735246 30.48 31 TiO2 3.73402 0.731311.61911124 27.1 32 SiO2 1.50756 0 1.14835805 47.61 33 TiO2 3.734020.73131 0.67754725 11.34 34 SiO2 1.50756 0 1.06599764 44.19 35 TiO23.73402 0.73131 0.623423 10.43 36 SiO2 1.50756 0 1.56705632 64.97 37TiO2 3.73402 0.73131 0.91482562 15.31 38 SiO2 1.50756 0 0.71403594 29.639 TiO2 3.73402 0.73131 1.50587943 25.21 40 SiO2 1.50756 0 3.98655573165.27 41 TiO2 3.73402 0.73131 1.45888837 24.42 42 SiO2 1.50756 01.46194734 60.61 43 TiO2 3.73402 0.73131 0.19291789 3.23 SubstrateGlaverbel 1.57857 0.00006 Total Thickness 1466.63 nr

TABLE 27 (Example D) In Reflection In Transmission Absorbance Y, % 39.0760.20 0.73 L* 68.80 81.95 a* −2.66 1.34 b* 11.49 −6.68

TABLE 28 (Example E). S-polarized light P-polarized light Average L*89.67 64.92 77.3 a* −3.58 4.24 0.33 b* −0.15 −10.42 −5.28 Reflectance75.59 33.95 54.77 (eye-weighed), % Transmittance 5.39 52.85 29.12(eye-weighed), % Absorbance 19.02 13.19 16.11 (eye-weighed), %

TABLE 29 (Example F). S-polarized light P-polarized light Average L*89.68 65.2 77.44 a* −3.65 1.11 −1.27 b* −0.13 3.29 1.58 Reflectance75.62 34.3 54.96 (eye-weighed), % Transmittance 5.34 52.46 28.9(eye-weighed), % Absorbance 19.04 13.23 16.13 (eye-weighed), %

TABLE 30 (Example G). S-polarized light P-polarized light Average L*89.57 40.6 65.09 a* −3.65 4.5 0.42 b* −0.26 −12.77 −6.51 Reflectance75.38 11.62 43.5 (eye-weighed), % Transmittance 5.71 77.51 41.61(eye-weighed), % Absorbance 18.91 10.87 14.89 (eye-weighed), %

TABLE 31 Example I Example H Eye-weighed Eye-weighed Eye-weighed ExampleJ Polarized average Thickness of Glass Absorption in Eye-weighedTransmittance Reflectance of Substrate/Extinction (Glass substrate +Absorption in an (PT) of embodiment embodiment of Coefficient of ITOITO), % EC-element, % of EC-element EC-element 1.6 mm/k 4.1 9.1 77.543.5 1.6 mm/0.75k 3.5 7.9 78.5 44.5 1.6 mm/0.5k 2.9 6.8 79.5 45.6 1.6mm/0.25k 2.3 5.6 80.6 46.7 1.6 mm/0.1k 1.9 4.8 81.2 47.4 1.6 mm/0.01k1.7 4.4 81.6 47.8  .5 mm/0.01k 0.6 2.1 83.5 49.9

As an alternative embodiment of the invention and in reference to FIG.30, an APBF 5310 may laminated between the back surface of a mirrorsystem 5312 (e.g., surface IV) and the LCD 5322 preserving its theentrance polarizer 5324 but having its exit, absorbing polarizerremoved. In this embodiment the APBF layer 5310 functions as the exitpolarizer of the LCD and increases the light throughput of the LCDdisplay as compared to a conventional LCD having an absorbing exitpolarizer. As an additional benefit, the placement of the LCD panel inoptical contact with the back surface of the mirror system 5320 reducedlight losses on reflection. This embodiment may potentially have by ahigher extinction ratio (defined for an LCD as a ratio of lighttransmitted from the LC-layer 5324 by the exit polarizing component tothat blocked by it), depending on the properties of the APBF 5310. Forexample, the current DBEF product of 3M, Inc. laminated between twoglass substrates provides an extinction ratio of approximately 28, whilethe use of another product, APF (also from 3M Inc.) increases thisnumber to about 43.

In additional embodiments of the invention, an APBF-containing mirrorsystem that utilizes an EC-element can be constructed with air gap(s)between an EC-cell and the APBF laminate. Such embodiments would berepresented by replacing a prism 408 in embodiments of FIGS. 4(F) and4(G) with an EC-element such as the element 840 of FIG. 8(D). The space435 would be filled with air or another low index material, giving theresulting embodiments higher reflectance in comparison to embodimentswhere the APBF laminate is in optical contact with the EC-cell.

In another alternative embodiment, described in reference to FIG. 31, anAPBF 5410 can be laminated between the EC-element 840, for example, anda surface V of the third lite of glass 5412 that is overcoated with areflectance-enhancing thin-film coating 5414 as discussed earlier inthis application. The other surface of the lite 5412, surface VI, isshown to be coated with a graded opacifying layer. A sample according tothe embodiment of FIG. 54 was fabricated for evaluation. The coating5414 on surface V was a three quarter-wave layer H/L/H stack includingTiO₂ (56.2 nm)/SiO₂ (94.2 nm)/TiO₂ (56.2 nm). Surface VI had a gradedChromium opacifying layer varying from essentially zero thickness in thedisplay (transflective) zone to approximately 50 nm in the opaque zone.It is understood, however, that generally a thickness of opacifying orOREL layer can be tailored to the specific opacifying material used andthe design intent of the final product. The opaque zone of the finalassembly had a reflectance of 70.7% (with a*=−4.8, b*=2.5) and atransmittance of 0.1%. The display zone had a reflectance of 64.7%(a*=−5.9, b*=3.6) and a transmittance of 21.5%. The polarizedtransmittance (that is, for polarization aligned with a transmissionaxis of the APBF 5410) in the display zone was 38.5%. This combinationof attributes, including the graded transition between the display andopaque zones, yields an aesthetically pleasing product.

Additionally, as has been previously discussed, once the laminationinterface has been formed according to an embodiment of the method ofthe invention, this interface may be optionally protected from oxygen,water, or other contaminants by having the edge of the laminate sealed.If necessary, the APBF may be cut slightly smaller than the substrateand superstrate thus providing a notch therebetween for the sealingmaterial to reside. FIGS. 50 and 51 show the location of the edge seal,denoted as “es”, for exemplary prismatic and EC-element typeembodiments, 410 and 850, respectively.

In other modifications, the reflectance-enhancing and opacifying layersof any multi-zone embodiment of an APBF-containing rearview mirrorassembly of the invention may generally be disposed in anypre-determined order adjacent at least one of the surfaces of thestructure to which the APBF is bonded, preferably adjacent a surfacelocated between the APBF and the light source. An APBF may substantiallycover only a transflective zone of the mirror structure. Alternatively,the APBF may substantially cover the FOV of the multi-zone mirrorelement. The transflective zone of the mirror structure may containadditional transflective layers. A light source may be part of thelaminate structure or a stand-alone component. All such variations andmodifications are intended to be within the scope of the presentinvention as defined in any appended claims.

What is claimed is:
 1. A switchable mirror system (SMS) for use in avehicular rearview assembly equipped with a light source transmittinglight from within the rearview assembly through said SMS to afield-of-view (FOV) outside the assembly, the SMS comprising: at leasttwo electro-optic (EO) cells defined by at least three sequentiallydisposed spaced-apart glass substrates, a first EO-cell corresponding toan outside portion of the rearview assembly and a second EO-celldisposed between the first EO-cell and the light source, wherein thefirst EO-cell is adapted to be a switchable linear absorptive polarizerthat attenuates light reflected from the second EO-cell, and does notsubstantially attenuate light transmitted from the light source throughthe second EO-cell, wherein said SMS has a reflectance value that isgradually variable in response to changes in voltages applied to thefirst EO-cell, and as measured in said FOV in ambient light, and whereinthicknesses of said at least three substrates are chosen to provide fora net weight of said SMS per unit area of less than 2.0 grams per cm².2. A switchable mirror system (SMS) according to claim 1, furthercomprising: first and second linear reflective polarizers disposedwithin said SMS so as to sandwich an EO-medium of the second EO-cellbetween said first and second linear reflective polarizers.
 3. Aswitchable mirror system (SMS) according to claim 2, wherein the firstEO-cell further comprises an EO-medium comprising absorbing andnon-absorbing states.
 4. A switchable mirror system (SMS) according toclaim 2, wherein at least one of the first and second linear reflectivepolarizers includes multiple layers of plastic film.
 5. A switchablemirror system (SMS) according to claim 2, wherein a combination of saidfirst and second linear reflective polarizers and an EO-medium of thesecond EO-cell is configured to substantially transmit light having afirst polarization and substantially reflect light having a secondpolarization when no voltage is applied to the second EO-cell, and tosubstantially reflect light having either the first or the secondpolarization when a non-zero voltage is applied to the second EO-cell,the first and second polarizations being mutually orthogonal.
 6. Aswitchable mirror system (SMS) according to claim 1 configured withinsaid rearview assembly, said rearview assembly further comprising atleast one or more of an illumination assembly, a display, a voiceactivated system, a compass system, a telephone system, a highway tollbooth interface, a telemetry system, a headlight controller, a glaresensor, a rain sensor, a tire pressure monitoring system, a navigationsystem, a lane departure warning system, and an adaptive cruise controlsystem.
 7. A switchable mirror system (SMS) according to claim 1,wherein the first and second EO-cells share a common substrate.
 8. Aswitchable mirror system (SMS) according to claim 1, wherein moleculesof an EO-medium of the first EO-cell change their spatial orientationsin response to a voltage applied to said first EO-cell thereby keeping atransmittance value of the SMS substantially unchanged during thegradual variation of said reflectance value.
 9. A switchable mirrorsystem (SMS) according to claim 1, wherein said switchable linearabsorptive polarizer includes an electrochromic (EC) element containingan orientated EC medium.
 10. A switchable mirror system (SMS) accordingto claim 1, wherein said switchable linear absorptive polarizer includesa guest-host liquid-crystal cell containing a dye, and wherein thesecond EO-cell includes a twisted nematic liquid-crystal medium.
 11. Aswitchable mirror system (SMS) according to claim 2, wherein the firstEO-cell is further adapted to be a switchable linear absorptivepolarizer that attenuates light reflected from the reflective polarizerin the closest proximity to the first EO-cell and does not substantiallyattenuate light transmitted from the light source through the secondEO-cell.
 12. A switchable mirror system (SMS) for use in a vehicularrearview assembly equipped with a light source transmitting light fromwithin the rearview assembly through said SMS to a field-of-view (FOV)outside the assembly, the SMS comprising: a first electro-optic (EO)cell defined by two sequentially disposed spaced-apart substrates thatcorresponds to an outside portion of the rearview assembly; and a linearreflective polarizer disposed between the light source and the firstEO-cell, wherein the first EO-cell is adapted to be a switchable linearabsorptive polarizer that attenuates light reflected from the reflectivepolarizer and does not substantially attenuate light transmitted fromthe light source through the first EO-cell, and further wherein said SMShas a reflectance value that is gradually variable in response tochanges in voltages applied to the first EO cell, and as measured insaid FOV in ambient light.
 13. A switchable mirror system (SMS)according to claim 12, wherein the first EO-cell further comprises anEO-medium comprising absorbing and non-absorbing states.
 14. Aswitchable mirror system (SMS) according to claim 12, wherein the linearreflective polarizers includes multiple layers of plastic film.
 15. Aswitchable mirror system (SMS) according to claim 12, wherein the linearreflective polarizers includes a wire-grid polarizer.
 16. A switchablemirror system (SMS) according to claim 15, further comprising: athin-film planarization layer overcoating said wire-grid polarizer, theplanarization layer having a substantially flat surface.
 17. Aswitchable mirror system (SMS) according to claim 12 configured withinsaid rearview assembly, said rearview assembly further comprising atleast one or more of an illumination assembly, a display, a voiceactivated system, a compass system, a telephone system, a highway tollbooth interface, a telemetry system, a headlight controller, a glaresensor, a rain sensor, a tire pressure monitoring system, a navigationsystem, a lane departure warning system, and an adaptive cruise controlsystem.
 18. A switchable mirror system (SMS) according to claim 12,wherein molecules of an EO-medium of the first EO-cell change theirspatial orientations in response to a voltage applied to said firstEO-cell thereby keeping a transmittance value of the SMS substantiallyunchanged during the gradual variation of said reflectance value.
 19. Aswitchable mirror system (SMS) according to claim 12, wherein saidswitchable linear absorptive polarizer includes an electrochromic (EC)element containing an orientated EC medium.
 20. A switchable mirrorsystem (SMS) according to claim 12, wherein said switchable linearabsorptive polarizer includes a guest-host liquid-crystal cellcontaining a dye, and wherein the second EO-cell includes a twistednematic liquid-crystal medium.